During the conflicts over the Chinese/USSR border in 1969 ( as well as their continuing disagreements over specific details of communism), the two powers nearly went to open war. The Soviets were considering a preemptive strike on China's small nuclear arsenal prior to a ground war. From what I've read, the US informed the USSR that use of nuclear weapons would likely lead to a worldwide war, so the Soviets backed down.
From what I've been able to turn up on the internet, China had somewhere around 70 nuclear weapons by 1970. So let's assume 60 in 1969.
With a POD of either:
1) The US makes no such threat as the above to the USSR, declaring neutrality
OR
2) The USSR laughs it off saying to themselves " the Americans will not go to war to protect a communist country"
What would be the effects ( short and long-term) of a nuclear exchange between the PRC and the USSR in 1969, followed by a full-scale conventional war?
Some interesting points to consider:
the effect on the Warsaw Pact and the communist hold on Eastern Europe
the Vietnam War
Soviet backing of communist rebels around the world
any others you can think of