Blocks and internals the same?

I have 2 318's, one from a 74 duster and the other from a 72 demon. Just wondering if they are the same or if one is better that the other. Both are low mileage, below 50,000 anyway. Got to get to know this small block stuff for my son. Im still out in the middle of the ocean, trying to gather as much info before I get home so we can get to work on it.