y5mgisi,
Maybe we can do this together :-)
Can you check on your truck and let me know what plug on the neutral safety switch puts out a 12V signal when in park or neutral? I would do it myself, but my wiring was a complete hack from the previous owner. I completely stripped it out and am using an aftermarket "hot rod" harness that controls the lights only. I didn't need the factory harness to do anything but the keyed ignition, lights, and wiper controls. The nice thing is, most "hot rod" harnesses use the GM steering column as a base, so it's a factory looking install.
I may try and put 12V things myself tonight, if I have enough time.