I've sonic tested a lot of blocks looking for a pattern and there really is none.....that I found anyway. I did find some thick ones. I will say most were 73 and back but there were some up into the late 70s that were thick. This was before I knew anything about the - numbers, so I did not include that. The 77 360 I punched .070 over for a 416 was thick. I don't remember the numbers as this was back about 1998 or 1999. Decent sonic testers are not too expensive now. If anyone builds any number of engines at all, it's a good tool for the tool box.
