the fix is in, and Bill Demmer is the winner:
Took the car to a local auto electric guru. His first words were "fuel problem" but when he heard that the problem would stop when the alternator was disconnected, he was intrigued.
A couple of hours of diagnostics and $127 later I had a new 12 gauge wire from the HEI distributor to the plug on the firewall, replacing the spliced connection to the original coil wire ignition system that was in place for at least the last 8 years. He thinks that perhaps when I replaced the coil last year, the new coil voltage draw is higher than the old, and when it gets hot it causes the problem. But he also said this doesn't necessarily make sense and was basically baffled as to what exactly was transpiring, since all his voltage tests showed things to be normal.
In any case, it's fixed.
