The 53 block in the 12v motors was a completely different part number and different casting than the dreaded 24v version. The 24v block they took metal away from the pan rail and side of the block to allow the motor to come to temp faster for emissions purposes and they stressed under load and cracked...
So its something that I need not worry about in the 12-valve flavor?? Good, saves me crawling under every truck I look at in the near future... :-laf