Once upon a time, there was a thin shim solid copper head gasket available- - - -.060" thick, IIRC. It was advertised as a "high compression head gasket" by places like J.C. Whitney. If the head and block sealing surfaces were perfectly flat, it worked OK, but I was always a little skeptical about the claims that compression could be increased by using a head gasket half as thick as the original sandwich-style gasket. On the alcohol-burning tractor pull hemi engines we used to machine a groove in the block for a stainless steel O ring and bolt 'em together with a thin copper head gasket, but those engines got torn down often, and the only place we ran coolant was in the cylinder heads. The water jacket in the block was filled with hard green epoxy to reinforce the cylinder walls.
Jerry
