Somebody makes Copper head gaskets for AMC, maybe it's SCE,
less than .040 thk, try http://performanceamstyle.com/
they may have'em listed, thier page is hard to go through.
Have heard said block should be o-ringed for use with copper.
There's a pair listed as .021 thick, $90
http://performanceamstyle.com/Cart/description.php?II=959&sessid=6f000356ad12d6d20bd677099f02557a&divi=amc