OK,

How flat do you really have to be for metal gasket? I am still toying with using a metal head gasket under a newly done drool tube head milled .100. This drool head would be replacing a peanut head that was built and milled .030 and put on a block that was milled flat Peanut head and block were driven about 100 miles with the peanut head on a Felpro gasket.

Is the block too warped now (never over 190 degrees and less than 100 miles) to try a metal gasket without re milling the block? I hate to give up that Felpro thickness, and besides, my Felpro leaked.

rock
64d100

I think getting the used surface clean will be the issue.
Once clean of old gasket material, sanding with a 'long board' and using a light coat of spray sealer should work well to seal it.
DD