If we get Someone Other Than Mao and they pursue a more rational Stalinist drive for industrialization rather than going off on tangents like the Great Leap Forward, and throw in a USSR which has rather more thoroughly de-Stalinized 1953-1970 than OTL, and hey, presto, they're the dominant Stalinist Power by default by the 70s.
Surpass the USSR as an industrial power? I'm not sure China has the natural resource base to industrialize as successfully as the USSR before the 1970s, using strictly Stalinist methods. On the other hand, if the Chinese did achieve comparable growth rates as the USSR 1921-1956 from '49, they might reach a level comparable to Kruschev's Russia in 1956 by 1984 (assuming that China's lower starting point is compensated for by Soviet WWII damage), where while still being rather poorer than the inhabitants of Zombie Chernenko's USSR, China's much larger population might give them a larger total industrial product.
(The likelihood of China duplicating Russian growth rates through comparable measures is left as an exercise to the reader.

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Just my 2 cents,
Bruce