2 barrel carb

Sounds like you have a problem with either the vent on the gas cap or theres a build up of contaminents in your gas tank eg rust flakes and other sediments is the fuel pump a mechanical or electric? there is a simple test to do to check to see if tank is the problem inside the tank there is a filter sock that sits in the bottom its purpose is to filter out lager sediment keeping it out of inline fuel filter . can you bypass fuel line at the tank and splice in a line up to the bed of truck put a jerry can in bed fill with 1/2 tank of fuel and stick fuel line in the can and you will need to open the line that attaches to the carb to let the air out of line after doing splice there will be an air lock tighten line at carb and fasten down jerry can drive careful you dont want to spill gas into truck bed . try this after leaving gas cap loose and trying , good luck think this will get you on the right track , and please if you find the tank is the problem take it out and clean it out dont leave jerry can in truck bed ok good luck let me know how it worked with a fixya decision please gotta love the good old carburator beets the pants off the electronic mishmash of sensors and wires

What year model is it I have a friend that had this problem, and it was a security code. the truck thougt it had been stolen.