Oldskool88

I recently purchased a '56 Olds 88 4-door post sedan. She's a beaut. Upon reading the forums on this site, I'm starting to get concerned that it isn't the original engine. Not a big deal - I'm not looking to do a pro restoration. But I am now curious and want to confirm that it is (or isn't) a 324. Although showing it's age, the engine paint is def. an aqua green (seafoam green) and not a dark green that I believe this engine should be. Isn't the aqua green an indication of a later model Olds? The carb seems correct: 2 barrel rochester 2V.

Where can I find the engine code on the block? And how can I decipher what I find?

Thanks!