My 235 runs bad at higher RPMs. Need help.

[NeverDone50]

Backstory: Everything electrical has been replace and updated to 12v. Point gap is .022, spark plugs brand new and gapped .035. Timing is set to 5 BTDC. I have two rebuilt Rochester 1 barrel carbs and the motor ran the same on both. Mechanical advance and vacuum advance work. Distributor is original, but cap, rotor, condenser, and points have been replace.

Here's what it's doing. The motor idles well. As you start driving it, through every gear at about the same RPM, it peaks and doesn't gain any more power. The motor sounds like its not firing right, either electrical or fuel related. Low end it seems to run great. I suspected bad spark plugs, so I got brand new ACDELCO plugs. Then I suspected the carburetor, so I put on another one. No difference.