Engine dies when hot, in gear

I run two pumps. A big mechanical and a Holly red in the back. Originally I was nervous about filling the engine with fuel if the diaphragm in the mechanical ruptures, but I have been running it like that for 10 years. A bit overkill on a street car, but there are several advantages. The first is if the car sits for any length of time the fuel in the carb evaporates out and you probably need to crank it FOREVER to start it. The electric pump will fill the carb in a couple of seconds. Another is REALLY stable fuel supply and my car will run with the electric off. So if the holley pumps dies I can still get it home. It won’t rev over 4000 rpm, but it will run. Finally to your issue, it keeps the fuel under pressure from the tank forward. A mechanical pump lowers the pressure in the line from the tank up to the pump inlet. Making the fuel boil at a lower temp. The electric keeps the fuel pressure at 5-6 lbs, raising the boiling point. The down sides are a bit complex install and noisy. Make sure your fuel pressure gauge isn’t a liquid filled gauge. They go nuts with changes in temp.