I would use the paper gaskets with permatex "high tack" the thin red spray gasket cement (tho the last couple of cans of it had specs of dried red material/something in the spray) if your bolt holes will still line up. People have used the valley pans as is as did Ma with no issues but vac leaks are the cats' a$$ to deal with. I would check that the mating surfaces on the performer are straight. As said there are several ways to block the crossover & I would without a doubt avoid E10 gas if you have a choice in your location. I think superformance has thin (.015") side gaskets available but you are already duplicating parts but the more info available the better. EDIT & iirc 440source (on the thin .015" gaskets)