One thing to try to do is go for is to keep your supply chain as simple as possible. So I would pick single state sources for types.
For example I would go all with American Aircraft for the Airforce.
P-51’s as fighter / interceptor / ground attack aircraft, large numbers would be available.
P-38’s (perhaps re-engined to us Merlins in place of the Alison) as the radar interceptor / night fighter
B-17 / 24 would be available in large numbers right after the war
If bothered with the Medium bomber role the B-25 is the clear choice
C-47/53 would available in large numbers and are an excellent design for transport role.
I would go also with American small arms, M-1 Garand’s, .30 and .50 Brownings, Thompsons as the SMG.
Armor and Artillery I would go Soviet.
T-34/85 as the primary tank, fresh built ones would be available. If was aware of the T-44 would got that instead but that’s unlikely. Use whatever tank chassis as a basis for a number of other uses such as.
SU-100 as a tank destroyer design, SU-122 SP Howitzer, recovery vehicles, flak designs, etc.
A standard selection of Soviet Artillery
Of course this type of setup would only work for a neutral nation but it would I feel have the best of all worlds.
