A bit like the fabled use of Chinese IS-2s, there doesn’t seem to be much, if any, evidence that the Chinese used SU-76s in Korea, at least in combat. The photographic evidence and captured trophies all relate to vehicles in North Korean service.
Still, they undoubtedly had some at the time of the Korean War and as it’s Bolt Action, I say your toys, your choice. At least with Bolt Action you are immune to cries of ‘fantasy’.