IMO, there's little difference between the 2 in strength. The roller block is a much better block to build and converting the older one to roller is a hassle and can get expensive, because of the cam base circles. Go with the roller. The heads and some of the exterior parts may interchange. You won't use the crank, rods or pistons from either. The cam, lifters, pushrods,waterpump, and timing chain cover are most likely not interchangeable. The heads are about all you might want to use off the 70's, to get higher compression, (depending on what you have), but going supercharged that may not be the best thing.