[mr0077]

Wheels, I ended up with the same situation, bought a 2x4 manifold to replace my Performer RPM single four...found out the manifold was a low-riser. I opened up the heads and port matched the heads and manifold, and WOW!, what an improvement over the 1x4. Note, though, that my dyno runs showed that the Edelbrock manifold was restricting my air flow, so maybe it was just the Ford 2x4 manifold. I'd do it the same way if I had it to do over again. I recommend opening them up, or (if you think the manifold won't flow well) get a medium riser manifold.