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What block, round cyl or square. There is plenty of clearance but not that much.Once it goes on the studs it shouldn't move.I have some base shims to lower compression but they are around .025"
Is it possible it has 850 cylinders sleeved and bored to 1000, but with the original 850 spigot diameter placed in a 1000 case? This would give (roughly) .045'' clearance.
Looks like he needs some convert cylinders..