Pretty much what I had in mind for them in my car world TLs, with a few modifications - Packard joins AMC in 1955, Studebaker following in 1960 or so as they started to flounder. around this same time, facing stiff price problems with OEM tires (a result of cutthroat bidding among the Detroit makers) AMC goes looking for a new tire supplier and Michelin bites, buying out Uniroyal and introducing its steel-belted radials into the North American market specifically for AMC. At the same time, AMC's engineers keep an eyeball over at General Motors, and are well aware of the ability to use more advanced technology to gain an edge on competitors, and AMC's use of Michelin / Uniroyal tires and Bendix disc brakes swells throughout the lineup as its customers come to very much like the feel of the radials and the far better stopping power of the disc brake cars.
AMC figures out that the long hood / short deck design mid-sized sporty car design Studebaker has in mind could score big, and shoves it to production as the AMC Javelin, introduced in 1962. The result is enormous - AMC sells every Javelin it can make for 27 months and rakes in over four billion dollars in revenue just on the Javelin, providing them with a vast nest egg. AMC's small car languish some as the Rebel, Ambassador, Marlin and Javelin models get the attention - but AMC also during this time develops a aluminum-block versions of its V8 engines with steel liners, considerably reducing weight and improving efficiency. By 1965, cash-flush AMC gives Packard a sizable sum to completely re-do its product line, as well as buying Jeep from Kaiser as the latter finally bails out of the car business. The 1966 AMX is equipped with either double four-barrel carburetors or mechanical fuel injection as well as capacitor-discharge ignition replacing the traditional cap-and-rotor cam-driven ignition system. The company also purchased the foundering American Locomotive Company namely for diesel engine technology and an electrical equipment and electronics division, Michigan Electric. (They'd be glad they did both of these in the future.)
The late 1960s sees AMC rapidly catching up with Chrysler, and Packard's series of new cars introduced in the 1966-68 timeframe are reasonably successful. But what hits hardest is the development of the I-4 and I-6 series engines, as well as VI-8 and VI-12 variants (which are effectively two I-4 or I-6 engines on a single crankshaft). These thoroughly modern double-overhead-cam, four-valve-per-cylinder engines are big for their size, but are soon known for smooth running, excellent response and prodigious power. The I-4 first sees service in the 1969 AMC small cars - the two-door coupe, four-door sedan and four-door wagon Hornet and the two-door hatchback Gremlin, the latter equipped with a Detroit-first six-speed manual gearbox among other mechanical improvements. GM's unreliable, flawed Vega and Ford's to-be-infamous Pinto are little match for the AMC twins, which in addition to excellent engineering are better-built than their Detroit rivals and are genuine competitors to the imports. The costs of all of the advancements, however, stretch the company, and while the excellent Hornet and Gremlin, the very good Packards, the fast-selling Javelin and AMX help matters, AMC finds itself having to chase markets for the Ambassador, Rebel and Matador, and the more expensive to produce cars don't help matters, though by the mid-1970s its clear that AMC's customer retention is as good as it gets, they face Ford's small car Hail Mary play in the Mark II Escort and Fiesta, and GM by this point was well known to be spending billions on a car meant to bust AMC in the mouth.
Enter Renault.
Renault's relationship with American Motors had been ongoing since the early 1960s, and by the early 1970s the two companies were partners in several developing markets, and by 1974 Renault was selling AMC products in Europe, namely the Rebel and Javelin, and they had a strong interest in the I-4 series of engines. When AMC began looking at the successor to the Hornet and Gremlin in 1975, Renault immediately jumped in, offering a massive cash investment into AMC in return for a sizable share of the company, co-development on platforms and use of its dealer network. AMC accepted the offer, and Renault took a 30% share in AMC in June 1977 despite howls over the cost from French unions. They would soon like the result, though - the Renault 9 and 11 twins became the Renault Alliance in North America for 1979, and the I-4E engine, now equipped with Renix fuel injection, electronic ignition and with a turbocharged and intercooled version available from mid-1979, proved to be more than worthy successors to the Gremlin and Hornet, while the AMC Spirit, which was similar in size class, moved to just a sporty fastback option, and in 1980 the Spirit SX/4 appeared on the scene, equipped with selectable four-wheel-drive and differentials that shifted power to the wheels with the best traction.
The results were immediate - AMC and Renault didn't quite beat the Ford Sierra to the market, but they did beat the rival GM J-bodies, Ford Escort and Chrysler K-cars. The newly-redesigned AMC Rebel became the Renault 21 in Europe in 1980 to more than a little success, and the Renault 22 / AMC Medallion twins, introduced in 1983, also proved to be sales successes. The Rebel was replaced by the Medallion and the Matador ended production in 1978, but the Javelin, Ambassador and all Packard models stayed with their engineers, but the Renault influence showed - and vice-versa was true as well, and Renault never bothered messing with the larger engines - indeed, they even began using them, as the highest-performance versions of the new-for-1983 Renault 25 executive car used the AMC VI-8 engine, and Renault's dealers in Europe began selling Packards there in 1981. (That start was far from auspicious, but it didn't take long for the cars to get a good foothold in the market.) The introduction of the Espace minivan to North America - badged as an AMC, and using the I-4A engine - came in July 1984, and it too was a substantial early hit, rivalling only Chrysler's minivan - while the Ford Aerostar and Chevrolet Astro / GMC Safari twins were coming at the same time, these truck-based vehicles had a very different vehicles to the Dodge Caravan or AMC Espace.
By 1986, the AMC-Renault deal had become a very different one than it had been ten years before, as AMC's already-excellent engineering had allowed Renault to make better large cars than before, while Renault was scoring in the small car market, while Jeep's SUVs and pickup trucks (most notably the Comanche pickup and Cherokee small SUV) were also sales success and Espace production had to be started in North America because the Matra plant in France couldn't even come close to keeping up with demand. The AMC Spirit had been one of the pioneers of four-wheel-drive as a tool for additional traction in a rally car, and it and the Audi Quattro destroyed their competition on rally stages in the early 1980s only for both makers to regard the increasingly-insane Group B rally car rules as a dangerous money pit. The Spirit began to be sold as a Renault in Europe in 1983, originally equipped with PRV engines. A supercharged version of the PRV V6 replaced the I-6 in the Spirit in 1984, and the car was redesigned as the AMC SX/4 in North America and the Renault Challenger in Europe starting in 1986. AMC's alliance with Renault had been followed up by Chrysler with Peugeot-Citroen in 1984, the Franco-American partners soon rapidly finding out that both firms had very large engineering assets. Packard by 1988 could sell one a medium-sized luxury car (a rear-driver with some parts from the AMC Ambassador, but mostly its own chassis), a large luxury car starting that year, a four-seat folding-hardtop GT convertible powered by the now-venerable Packard-AMC VI-12C4 engine. The combined company even began selling Renault's car-based vans in North America starting in 1984 for the Jeep V100 (a rebadged Renault Trafic) and the bigger Jeep V150 (based on the Renault Master) starting in 1986, while the Jeep Comanche pickup began sales in Europe in 1986.
By 1990, the two companies were intertwined, and when Renault was privatized in 1994, AMC bought a big slice of it to act as a counterweight to Renault's influence on the American firm - not that Renault minded that much. The number of AMC-Renault-Jeep-Packard dealers in America had swelled from 1450 in 1978 to just below 2000 by 1994. The second-generation Alliance, introduced in 1988, kept up the sales of Renault's small cars, and the introduction of the tiny Renault Clio in 1990 and the even-smaller Twingo in 1992 proved to be unlikely successes for the firm, and by the mid-1990s franchises for the alliance makers were in demand. The 1992 Jeep Grand Cherokee slugged it out with the Ford Explorer for sales in the booming SUV markets of the 1990s, and while GM, Ford and Chrysler all largely focused their attention on trucks during this time period, that wasn't possible in Europe and AMC felt it was unwise, allowing its ever-improving line to grow its car sales. AMC ripped off a milestone by having its first everyday car in the latest AMC Medallion be among the ten best selling cars in America in 1995. Perhaps the biggest single symbol of the company's awesome prosperity was its move out of Detroit, taking over much of the space in the former Sears Tower in Chicago starting in March 1997 and when Sears' naming rights expired in 2003, the tower became known as the American Motors Center. (AMC ultimately bought the building outright in 2008.)
The biggest moment for the two companies was when the two teamed up in 1999 to buy massively into the nearly-destitute Nissan, gaining access to many new designs and Nissan's vast presence in Asia. At the same time, Renault bought Samsung Group's automotive assets, financing this by selling off a number of assets to American concerns - AMC bought the bus division to allow its own such operations to gain market share, Renault's industrial automation division was sold to machine tools maker Cincinatti Milacron, it's specialist engines and engine parts division to American firm Elan Motorsport Technologies, it's logistics operations went to the Southern Pacific Transportation Company and John Deere bought the company's agricultural equipment division.
The alliance between AMC, Nissan and Renault allowed AMC to retire the descendants of the I-4, I-6 and VI-8 engines in favor of Nissan units for the V6s and joint-venture units for the inline-four and V8 engines. The acquisition also allowed Nissan's struggling pickup truck division to be sold off to AMC while the SUVs remained as Nissans, and Nissan's Infiniti luxury-car division became a much more overtly sporty one after the alliance so as to not run into trouble with Packard's lineup. (Nissan and Packard teamed up for a new big sedan, called the Nissan President in Japan and some parts of Asia and the Packard Executive just about everywhere else, using Nissan V8s or Packard V12s depending on the market.