old school 340 cam help

I don't see an .083 gasket in the on line look up but there are several .086 and .080
one has a 4.080 bore for his 4.070 bore motor
not much crevice more than that on the piston down to the top ring
I guess he could use a shim and a gasket like the re-builders do (even worse)
He could open the chambers to 4.070 to get the compression down or others have suggest cutting the pistons
Evidently someone sold him on the 318 idea
and evidently there is no going back on this build--
he has not said what happened to the old heads