Steel shim OE gasket. Just me I'd either clean the surfaces up & use the thin composition gaskets that are available & button it all up or clean it up & have the surfaces checked for flatness & use steel shim gaskets with alum spray paint which steel shim ones require flatness. Probably be better to check for flatness since you're already apart & you dont want to have to go in there again & I think I would go with the thin composition ones. Holler how it turns out