Sub note: Torque increased everywhere., starting at the lowest testing point, 3000 rpm.

Headers do more work than just reducing flow restriction. The "tuning effect" of long tube headers cannot be denied.

Here are two more thoughts:
1. If I were going to do a story on a 383 with a HE285XL cam I'd start the dyno at 3000 rpm, too. That's quite a big cam for the engine, too big for the street.

2. AndyF had the best results using the MP .528 cam with HP manifolds. Assuming the cam events were the factors resulting in success, would it make sense to have a custom cam ground using those same events but with higher lift? Much work has been done on optimizing cam lobes since the .528 was designed.

R.