Sometimes it's the simple things that bite us in the rear axle. I see timing has been mentioned several times, have you thought about a bad coil? Most times a bad coil will not be able to produce enough voltage under load to keep the engine running.

Try this. Get engine warm, drive truck in high gear at a slow speed. (lug it) then romp the throttle. A coil that is marginal will usually crap out then. This test doesnt work in neutral, engine must have a load on it.

Good luck