The 428 industrial blocks that I picked up from this guy run the gamut from unmarked to one with the C scratch, one with an XJ scratch, one with a CX scratch, and a couple with a C1 scratch. Most have the ribs on the outside, but two don't. In all but a couple cylinders the sonic data shows that on the thrust sides of the block the walls are pretty thick, well over 0.125". I'm beginning to think that despite all the external differences, the blocks are more alike than they are different in the key areas, despite the markings or sand scratches...