just check it out...this guy is a reputable poster on another forum I frequent more often than here. TMeyer Projects - 302 Overbore bored a 1988 block 0.125" over just for chits n giggles
I asked him if he still had it kickin around and if he wouldnt mind scopin over it a little more.That was not an aftermarket block. Just a late model block.
We were just playing around, we never did check it all the way around and up and down the bore.
Ive youve never heard of anyone going more than 60 thou then its impossible for you to say its impossible...as you have no direct personal experience.If it's a stock block with no tricks, it's not possible. I've never hear of anyone going beyond 60 thousandths.