After reading this thread again, I suggest replacing the ignition switch. It may not solve the problem for good, because there may be too much current going through the switch. But if it gets the truck running reliably for a while, you could then check for other symptoms. It is hard to fix something that wont run. I think the run contacts in the ignition switch are bad, causing low voltage on the output side of the switch. When you turn the key to the accessory position you then have full voltage for things like the wipers. So just buy the switch, but not the lock part.
Larry