RTV works wonders. I'm not a fan of the older (read: VERY THIN) felpro gaskets, but most modern ones are perfectly fine. Cork gaskets do tend to leak a little, even from a fresh install -- I had them on my Turbo Coupe for the valve covers. Get yourself a good brass brush and clean up the areas where you will be using the rubber/neoprene gasket and then use RTV or gasket maker in the trouble spots like loudsho recommended. None of the parts stores I deal with still carry the problematic cork gaskets, you may find them at really ancient parts stores that are not affiliated with a national chain.