I've used the "thick" Fel-Pro gaskets mentioned above, but like fast68plymouth mentioned, they delaminate (peel apart?) during the first disassembly.
If my standard Superformance VC gaskets have any sealing issues w/ Indy cast covers on Edelbrock Victor heads (something odd about the Victor's valve cover rail, as I recall from AndyF), then would the Carbon-X be your next suggestion?
If you have the Superformance #3186 Micropore-15 valve cover gaskets check and be sure the valve cover sealing surface is flat. You won't have any issues.