Lets say the blocks bores do match the gasket bores. If there is no apparent clearence between piston and the metal gasket rings, I'd think you'd have a problem once the gasket is chrushed. It will indeed crush to 0.032"/0.8mm and when it does it will, like Phil already said, indeed decrease the bores diameter.

But lets say you'd have a block decked so the piston are clear with the deck. When revving it the pistons will rise .030-.032" (Phil's numbers). What would happen if one would just cut the piston a bit, so the top .035" of the piston or so will have a smaller diameter, lets say 3.600" ?

Or will this back-cut area be filled up with carbon deposits in no time and still cause a problem at high rpm's? (when constantly revving it to high rpm's there will no problem (I think). But what happens when this engine would be a daily driver and only once in a month be revved to those high rpm's?
But then again, it's exactly the same situation with the carbon that's on the head's quench area is it not?
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)