Had to tow the 69 home yesterday.

[Syco67]

Got a call from my sister, the 69 GMC had died. She said it started hesitating, and backfiring out the tailpipe, had no power, then it just died. It was pretty hot out, but the temp gauge stayed on the low side the entire time. The truck sat for an hour before I got there with my trailer. The truck started and ran fine to get it on, then I towed it home. What can I look at here, we had the same problem last year. I was thinking vaporlock. WE replaced the carb, fuel pump, filters, replaced and rerouted the fuel line, adjusted the points/dwell, Cap/rotor/wires/plugs are still pretty new, 4 core radiator, water pump, t-stat. When it's cool out, the truck runs awesome, but when sitting in hot traffic, this always happens.