All have a "352" cast into the drivers side front of the cylinder block.
427's are easy to ID by the cross-bolted mains, and if there is a oil gallery rib just above the oil pan (forget which side), it's a side-oiler.
If the date code of the block is 1965 or earlier than it can't be a 428, it's a 390 or 352.
428's are externally balanced so the flywheel will have a balance counterweight on it. 390 and 352 are internally balanced, so you have to pull the pan to take a look at the crank, and while you're there you can