I wouldn't just got throwing parts at it hoping to fix it....that can get expensive.
To me, it sounds like you've got a bad set of plug wires. Typically bad wires will cause a misfire under load while at a cruising speed on the highway, etc (say you've got cruise control on and you go up a hill on the highway - the engine will start to miss.) An easy way to check this is to get a spray bottle with water in it, go out during the dark, have a buddy sit in the truck and LIGHTLY brake torque it. Spray the wires/coil/dist. cap down with the water, one at a time. If the truck begins to miss and run like crap when you spray the wires (more than likely they'll arc externally and you'll see it - which is why you do it in a dark setting) then it needs wires....if the thing runs like crap when you spray the coil, it's going to need a coil...etc, you get the idea. But that's only going to work for the secondary ignition system.
If that leads no where, I'd say pull a plug, and look at the gap. If it's huge (spec should be around .060 I *think* - should be a sticker under the hood with it on it) then you're going to need plugs.....
That'd be a decent check of the ignition system. If that doesn't yeild anything obvious, i'd say go to the fuel system. First thing to check if you were a tech would be fuel pressure as well as volume. To do this you'd need a fuel pressure guage. If they're good, then I'd start looking into bad injectors/pulse width signals. If they're bad, I'd check the filter, to make sure it wasn't plugged or restricted at all (take it off and try to blow through it, also make sure you see what comes out of it - is it dirty?) If the filter's fine, the only thing left would be the pump.
You've got to check the obvious first before you can start doing things like checking injector ohms with a volt meter....
Cliff notes: Check the wires/plugs, take the fuel filter off and try to blow through it - or just replace it cuz they're cheap and it probably needs one anyhow for preventitive maintenance.......then let us know what you find