Are you talking about the actual engine the car was shipped with ? Are you sure it didn't go to a scrap yard ? No way to find it other than posting want adds everywhere and hoping somebody even reads it and/or knows what the engine number is/was.
I was think maybe going through the previous owners and just tracking back trying to find out when they remove the original 360 or what they did with it the block will only have the sequence numbers of the car correct