I've got a vapor lock issue that I can't seem to fix.

The engine is a 1977 360, stock heads, Summit intake, Edelbrock 1405, and Headman headers. Running Vintage Air. Three core AL radiator with full shroud and electric fan and 160* thermostat. Engine runs cool, normal 170. Gets to 180-185 if sitting in traffic with AC on. It does get very hot under the hood with the puller electric fan. This all in a 1953 Ford F100 panel truck

For the past few weeks when it's hot (90-95*) the engine will vapor lock if I drive it for an extended period. When engine is cool it starts and runs fine. Even hot re-starts are no problem. However, if I run it for a long run with the AC and the engine temp gets up to 180* it will die. When I look under the hood the small in-line Mr. Gasket fuel filter up by the carb is empty. No amount of cranking will re-start. Tried to vent the gas cap and removing fuel line, no help. The only way to get the engine to re-start is to allow it to cool some and then dump some gas in the carb to prime it. If I just let it sit for 2 to 3 hours the fuel filter refills and the engine will start with one or two pumps. I can repeat the problem by letting it idle with the AC running for about an hour and then it will die and fuel filter will be empty.

I have tried the following: new electric fuel pump (Holley 12-125) mounted next to fuel tank. One inch plastic spacer under the carb. Re-ran all the fuel line away from headers. Came along the floor and up the fire wall with all new 3/8 fuel line. Tried to keep fuel line out of engine bay as much as possible. Line comes from behind distributer to back of carb. The only original fuel line is about 18" coming out of the tank.

So, where do I go from here? The only things I can think of don't seem likely to help. Rebuild carb? Insulate the fuel line? Is there a way to ventilate the engine bay?