It looks like your friend's plan of preventing hot-wiring is working. I think you would have to trace all the wires, and figure out how his wiring compares to the original wiring, and toggle the switches to appropriate positions or eliminate them. Somebody trying to steal the truck would presumably not have ample time to figure all that out and get it started before somebody walked outside with a shotgun or turned the dogs loose. :-)
The wiring:
http://67-72chevytrucks.com/vboard/s...&postcount=302