one block is bigger than the other, it's pretty much how it sounds

has nothing to do with displacement, think of it as a family of engines

for the most part i can't swap parts from my small block 360 to my big block 440 due to different dimensions of the actual block. The small block stroker engines are what cause most the confusion. Some of these stroker blocks have as much displacement as the big blocks.

hope this helps, can't really think of a better way to explain it.