Check the rubber fuel line that goes from the frame to the fuel pump, have had them leak and suck air, thus not delivering enough fuel. If you have the old fuel filter that screws into the carborator these become cloged and not enough fuel to carb bowel to run truck. Its a good idia to replace it even if you can blow threw it, the filter that is. I have poked them threw with a scew driver just to get me home when they become cloged.
good luck.