There is a pad on the deck just above the pass. side top water pump bolt as well as maybe one right above the middle of the top of the water pump pulley..
On the pad(s), there should be a string of numbers and letters.
Post the letters b/c they decode the engine size to year and type of vehicle, (and possibly carb. and tranny type), the engine originally was in when it came out of the factory.
If the number/letter string isn't there, the block has been decked and you can't tell what it actually came out of.... (SOL!!!).....
I love it when I go to car shows and the Dude says all original, but the motor has been decked and has no ID code and then has the wrong valve covers and pcv on it thing!!!!