Actually if you're having problems with the copper gasket sealing the black gasket may not work either. If the block deck is warped and the head surface is out then the only solution may be to get some machine work done.
We just got in an engine that the deck was warped but the head was resurfaced with the black gasket and the gasket couldn't hold the water back from leaking.
A gasket is sometimes only as good as the surface.
www.jandm-machine.com