Everyone loves an update... so here it is.
I found the problem.
Since I had done everything else, the only thing left to do was to rebuild the carb. Factory date code tag still on there, ordered up the kit. Pulled the carb, immediately saw the cause of the issue. The base gasket had failed on one corner, allowing moisture and rust to accumulate on one small area. I believe that once hot, unmetered air was being pulled below the carb causing an ultra lean condition when the throttle was opened. It was obvious that this had been developing for a long time. If you know 4GCs, you know the recesses on the base, one was all full of rusty/carbon/crap.
I could have simply cleaned up the base, and re-gasketed, but... I had the carb off, so... I rebuilt it anyways. It was spotless inside. Cleanest carb I've ever done. I can't say enough about using non-ethanol gas. Zero deposits inside, non of that white powdery buildup that you see from ethanol gas. Set the floats, reinstalled. Nice fresh carb base gasket, made sure the mounting flanges were clean and square for a good seal.
Verdict? Car is driving perfectly. Lots of power, all the way through the RPMs. I started with a couple mile drive around my house, then a 15 miler to town, then a 40 mile to work and back. All is good. And I have a new fuel pump, and electronic ignition, lol.
Bottom line? Once you've done everything else, the answers get easier to find.
Two doors, four doors, wagons, and ragtops.