Thick.

Had my MP replacement block sonic tested before boring. I don't have the sheet here, but I will post the numbers. Numbers were taken at the thinest (about 2/3 down cylinder) part of the block. Above and below this area, the cylinders are, or almost simese. Average thickness on the major thrust areas were consistent at .400" with the minor thrust around .350". Between the cylinders, the thinest was .170".
I think we have room for a couple of rebuilds.