Engine identification

When I bought my 66 B'cuda the engine and transmission was replaced. The 273 w/auto was replaced with a 360 w/ auto. The information on the source for the engine is long forgotten/misplaced. I believe it was from a 72-75 Mopar.

Before I start sourcing parts for the car, mainly ignition, I would like to get more information on year etc. the engine was produced.

What is the best way to determine what I've got?