8f12 = June 12, 19?8 C80E tells me the question mark is 1968. This is the day the block was actually cast. If you look in the circled area below, there may be a partial VIN stamped there. If so, post it and it can narrow down significantly what type of vehicle the engine was originally out of.
8A271049 if the block was cas cast in 68, i don't think it came out of this car. when i got it it had 50's for back tires and there was signs that someone had been drag racing this poor thing.
8A means a 1968 model year car built at the Atlanta (Hapeville), GA assembly plant. Probably a Torino or something. The car's VIN that the engine was originally from looked something like 8A??F271049. Question marks would be the body identification code, which I couldn't tell without knowing exactly what type of car and body style it came out of. That number would match your car's VIN if it was original.