Assuming we have the nuclear test in 1975~6 (with only Taiwan declaring itself as a power, since ROK was negotiating some nuclear technology transfer), we'll be seeing Mao right before this death looking at what would seem to him to be a conspiracy by the US of invading PRC. Since he is probably going to die around the time he did in OTL, we might have Deng be shut out from power as the hardliners gain power using fear of ROC as a weapon. Basically, the market liberalization might be pushed back decades or perhaps indefinitely, turning the PRC into something akin to Burma.
This wouldn't be a pretty world. Leaving out PRC, the USSR is probably going to be more aggressive towards the ROK/ROC alliances, while the US would most likely be angry with both of its East Asian leaders.