AD Pickup,
People have reported that CA is a state that liked to have an ID stamped into the frame (GM did not do this from 47-55, at least). However, people have reported IDs being found stamped into their 47-55 frames from CA. Have you looked at the frame rails to see if a code is stamped anywhere? It would be interesting if you found a code that matched your engine code. The person/shop that put in the replacement engine might have followed the CA rules for changing the registration/title ID.
By the way, the engine/head casting codes are quite helpful in identifying an engine; but, head and block casting codes were sometimes used used over multiple years. Date casting codes are also quite helpful in identifying the pedigree of an engine.
Here are locations of casting codes for a 1951 low-pressure 235 truck engine. I do not know if 235 car engines have these codes in the same locations.
