I think there is a mix up on numbers---.003 is not enough warp to not seal---0.03 is enough for a leak--also if you take some off the head side you will probably need to take some off the bottom surface so the ENDS don't hold it up so it don't mate with the heads.

Some old timers used to cut the end of the block an amount coorsponding to the amount taken off the deck surface so manifild sealing wouldn't be an issue---for instance--I had 3 different manifolds that I ran on my motor, so trimming the block was the way to go--