As it has been said earlier, it could be a wide range of things happening.

A: Could be a fuel delivery problem. Either not enough or too much fuel.
A Wide range of things can cause either too much or not enough fuel reaching the engine.

Not Enough Fuel:
1: Filter clogged. Either the engine fuel filter or the filter in the tank being clogged.
2: Fuel Pump Bad or defective.
3: Fuel Pump Essentric worn out.
4: Bad Fuel Hoses, or lines, colapsing, kinked or leaking causing vapor lock.
5: Vapor lock itself. (But will rectify when engine is cold untill it heats up)
6: Defective float valve not allowing fuel through.
7: Bad Evaporative emission components (If Applicable). The fuel tank and carb vents through the evaporative emission system. If it's been plugged or disconnected the tank or carb might not vent causing vapor lock.
8: Simply running out of gas in the tank. You may need to prime the engine, pour a little fuel or starting fluid in the carb's air horn to get it to fire the first time. That and add fuel to the tank.
9: Fuel Selector solenoid defective. (Only on trucks with two tanks) Is there fuel in both tanks?

Getting too much fuel:
1: Defective float or float valve in the carb. The float valve sunk to the bottom of the bowl causing a flooded condition. Or a stuck open float.
2: Defective or wrong application fuel pump, pumping too much pressure to the carb or leaking fuel into the engine oil.
3: Defective or worn out carb in need of replacing or rebuilding.

B: Could be a spark problem.
1: Bad ignition module,
2: coil
3: distributor component, magnetic pickup. Bad Cap and rotor, plug or coil wires, etc...

C: Catalytic Converter plugged or plugged exaust.

As others have said, find out if you are getting fuel, or too much fuel, and if you are getting spark, then work from there. Good Luck.

 

Thanks,

One thing I was wondering - I'd driven it down to my dad's work and back once before. It died when I got there and twice in town once I was back. All three of those times if I held the gas pedal to the floor, it would restart. When it stalled on the highway on Saturday, it cranked over slowly. Plus, this time it wouldn't restart at all (well, for one second it did).
I will check all the things on the list, but it just doesn't make sense why it would always restart before, but not now.

Edit: Just wanted to let all of you know, the engine in my truck isn't the original engine. If this makes any difference, please let me know.

 

I didn't see anyone suggest to check the choke for sticking closed. Will cause the exact symptoms you describe. OBCB

 

Good Catch. oldbrokecowby.

That would definately cause a flooding condition. Sometime you can overlook the simple stuff.

 

Yah, thanks!

I'll let you all know what I find out on Friday or Saturday. I've been very busy the past few days. I'll be able to work on the truck Friday evening.

I hope it is something simple. All I need now is to find out that my two week old, $800 truck is going to nickel and dime me untill I'm finished fixing it up. If that's the case, I might as well park it and rebuild the thing from the ground up. That way I'd know each nut and bolt is tightened the way I want it.