soooo...
on GM motors, I often suggest adding an oil pressure switch to the ignition circuit if the time delay does not do the trick,,, but as this is a tier 2 truck, and the computer does the same thing by reading the crankshaft sensor, I think there may be a different problem that is not really ignition related, but mechanical to the starter-ring gear. I would suggest that the ring gear is _carefully_ eyeballed, and _complete_ tuneups done, regularly. also checking to be sure the key switch requires complete turn off before returning to 'crank' from run.