Since I guess you can not sonic check it for thickness, I like to look at the boss where the cam bearings are machined. If the boss is off to one side compared to the actual cambearing hole, I suspect casting shift, and would have it sonic checked before using. Their used to be a number cast into the block that told how many times the mold had been used. The idea was the lower the number the less likely core shift was, but I never had much luck with it working out.