The Stovebolt Site Forums The Shop Area Engine Shop 235 , Good compression, black sooty plugs, runs good

Finally getting around to doing some troubleshooting / verification on the 1954 3604, 235 with 216 Intake/exhaust manifold and Rochester B Carburetor. It starts and runs fine , I think. The idle does not drop from fast idle without bumping the accelerator pedal . Seems to throttle up nicely without any bogging. The tailpipe is black and sooty and so are the plugs. Here's the compression check info and pics of the spark plugs. Is it running rich? What's the recommended solution. Timing is set at 3-4 degrees advanced, mixture screw set using best vacuum method. Running non-ethanol 91 octane fuel. Advice/ suggestions requested.
1. 135 psi
2. 145 psi
3. 145 psi
4. 145 psi
5. 147 psi
6. 149 psi
Checks done with Engine at operating temp, using screw in type Compression Tester, throttle at WOT. All plugs removed. No oil added.
Plugs are pictured 6,5,4,3,2,1