help! what engine is this?

[newin72]

my dad bought this suburban new in 1972. He has always considered it a 350 motor. but tonight, when I went to 3 different auto parts stores, the motor mount didn't match.

so for kicks and giggles, we went and got the motor mounts for a 327/305 and it was the right one!

what is the best quickest way to find out what motor this is?

it is out of the truck right now awaiting the installation of my new ZZ4, but I don't know where to start to find out what I've got.

Thanks!