This is all going from memory, but I recall reading about IS-2 / ISU-122 afvs in two places. One was in one of Ballenger's books in which they were photographed in the neutral zone near Panmoujon (sp?) and the other was in the book written by the Marine who kept a diary during the last year of the war. He claimed that his position would sometimes get a volley from a 'Stalin' tank the Chinese kept hidden in a cave & would roll out occasionally. One time it rolled out, a Marine M46 was trained on the position & got a round off at it before it rolled back into the cave. Can't think of the book or author.
Somewhere on the web is a translation done by Cookie Sewell of a Soviet account of Chinese armor in the war. iirc, the Chinese had a small number (low double digits) of Stalins toward the end. I assume if they deployed them conventionally, the USAF would have toasted them
ed: it's "The Last Parallel" by Martin Russ