I've got a '77 440 that I'm going over and will be replacing the steel shim head gaskets with an NOS set I've had for years. I have scraped the deck surface with a razor, but still have some sort of imprint on the deck:
77_440_Gasket_Print by clair_davis, on Flickr

The imprint almost seems like it's part of the tin plating or something from the shim... it doesn't seem to come off with a razor, but I can feel it if I scrape it with my fingernail. What do I have to do to get this stuff off, or do I need to worry about it? I would guess it's a couple thousandths thick if I can feel it, and with an 0.020" gasket, that might be too much to leave behind.

Thanks,

Clair