Stu you would not want any gasket overhang as that would add a restriction for no good reason & defeat the purpose. Since you have em on hand could you cut em out to match your ports. No opinion if copper is significantly better but I'm sure they would be more pricey & I'd sure think they would be better. Not sure what'd be the best sealer for them. SCE wanted me to use Indian head gasket cement (the thin brown stuff with the shoe polish type applicator) on my solid copper head gaskets