86 Chevy 3/4 PU 5.7 vapor lock symptoms (hesitation like fuel gaps) but I have done all the normal remedies - rerouted the fuel line -?

rebuilt the carb (with new filters) replaced fuel pump. It happens when outside temperature is near 100º

Is it possibly connected to the fuel tank? I have never been able to put more than 13 or so gallons (about 3/8 tank and I have run dry so I know the gauge is working) the last one with great difficulty due to auto shut off on pumps.

Is there some sort of internal blockage or somehow a pressure/issue connected to this tank problem? Somehow aggravated by the road heat? Ambient 100º+ temps?

I can often work through the hesitation problem by feathering the accelerator and at its worst I have been able to continue on after 1/2 hour wait or so... and after the temperature has dropped (evening)

Help!