Finally! Here's my Fish!!!

Quick question about the engine. I would assume the short block that was installed in 1975 was probably new back then. If I were to attempt to locate a correct year 225, how difficult would my search be? Or would I be better off just re-doing the engine I have and leave it at that? Thanks in advance.

I have on in my 65 but don't know the code also have a Super Six 2 bbl too