I measured my Performer 390 one inch higher at the flange. It is also narrower, so if you want to use the ford spacer with PCV, it won't fit without leaking underneath. If you are thinking of getting an Edelbrock carburetor, now would be the time.
Mine was port-matched to C4AE heads but I think it would have fit fine without that. I added a water sensor port and had to rebuild two other threaded openings. Used the cork end seals, trimming the tips 45 degrees, and they are doing fine. Valley pan, distributor, throttle bracket... all fits fine.