Re: 72 Mustang 302 dies when hot.
Thanks for all of your helpful advice. Here's the outcome of some work this weekend:
1. Fuel WAS boiling, and causing some undesirable issues as you would expect. Put on a 1" phenolic spacer, along with heat shield under carb, and a reflective thermo/insulating sleeve around the hard fuel line from the fuel pump to the soft line at the carb. Made a huge difference. Also went ahead and put a heat shield between the exhaust pipe and the exit line from the tank, since that line was about 2 inches from the exhaust pipe.
2. Although it ran much better without the vaporization problem, after a few cycles of running the engine around with the A/C on in stop and go traffic, and then turning the ignition off/back on, I started getting some stumbling. It wasn't as bad, so I kept on doing it for another 20 minutes to see if I could make the problem worse—got to the point it would not even restart after sitting a couple of minutes with the key off. No spark.
3. Was running 12 volts to the NEW Mallory resistor coil, as recommended by Mallory. Instead, went back through the resistor wire, to a standard Accel coil, and have been running strong all weekend long, through SUPER hot air temps. I don't think the resistor coil was letting enough voltage through after it heated up.
SO, the problems were multiple fuel and electrical issues.
Thanks for all the replies and suggestions. I'm sure I'll be back!