thin cylinder walls on a 440?

There are no "thin wall" 440 blocks. One of the magazines had blocks tested several years back and the walls are the same thickness.

BUT........there are some stiffening ribs on the outside of the block that were left off of the later blocks making them a bit lighter. I would guess that wouldn't matter unless you were wanting to build some monster piece for racing. Then you would probably use a block filler which would fix that issue.