if i had worked on the truck i worked on yesterday and knew what i found out on these trucks i may have suggested looking at the ignition wiring. Yesterday i had one of these that would start and run but ran crappy when accelerated, missing and cutting out....
turns out it was the same problem that you found, the wires to the distributor were previously repaired with a half-aced splice job and the wires were coming apart and had rubbed and gotten exposed.
I repaired the wiring and the truck ran like a champ afterwards ;o)

good job bowler