Truck keeps stalling out please help

[68 Donkey]

I have 68 C10 with a mid 80's SBC and a 350 automatic transmission. Everything on the engine is new expect the fuel pump and plug wires. My problem is the truck will run fine for a few miles then it begins to stall. I work the gas to keep it running. The problem is intermitting and the engine may be hot or cold. We have set the timing and vacuum. We idle it up because it wants to stall when put in drive. I went as far as having the torque converter checked.
The Quck fuel carb is brand new too. Please help. Any suggestion appreciated.