Stroker, as you mentioned, the major thrust side is of the most concern. I always tried to select a block that would be at least .125 or thicker in that area for race or HP use, after it was finish bored. The 250 blocks do seem to be a little thicker than the 292's for some reason. Also, as you mentioned, the area between the cylinders seem to be thinner as well, but I still would try to maintain at least a .125 thick as a margin for use. As long as I didn't find a spot that was bigger than a quarter that was thinner than .125 directly in line with the major thrust, I would consider it for use if it was perfect in all other areas as in magnaflux. Now thats not to say you couldn't/shouldn't use a block that is thinner than that for street use or mild recreation. I also would never use a block that had or required a sleeve for a race engine. And again, not to say that one needing a sleeve couldn't/shouldn't be used for street or mild performance use.
