1972 350 Chevy c10 won't start

The dist was either installed wrong, vac advance not hooked up, or base timing is off, plug wires installed wrong, I could go on and on. When you try to start it, does it smell like raw fuel? You could have even flooded the engine accidentally while working on it. Have someone crank it while you look down into the carb and see if it's getting fuel. If it is, and its flooded, do this. Get in the truck, start cranking the motor, and WHILE it is cranking, not BEFORE press and hold the pedal to the floor, DO NOT PUMP THE PEDAL, just crank and hold. That's the old timers trick. I'll be really honest here, most of the folks on these boards are dealing with injected cars, and carb stuff isn't as easy to diagnose as the codes spewed out by a reader. Let us know what you find.