Jim, I have the thicker copper head gaskets in my engine to make up for cleaning up the head gasket area. No need to shim, just get the right size based on how much you cut off. Ned Madsen 1965/6 Corvair Monza/Corsa 140 (soon to have AC) CORSA Member since 2000 Mid Continent Corvair Association - President Great Plains Corvair Roundup - chair