The GMC is one of those engines that you don't have to look up serial numbers or cast numbers to ID them, they have the cubic inch stamped right on the distributor pad, 228,248, 256 etc.....
Many things will interchange between all these engines, but the most critical thing is the head swapping. Some of these engines have domed pistons and most every engine cubic inch group had a different combustion chamber size and shape to match its engine. So you just need to be careful if you start trying to do head swaps.
