or you could worry even less and attach the wire to the reverse lights that are already in the back of your truck. take off one of the light covers and test which wire turns to 12vlt when you put the tranny in reverse and then you wont need to run 4ft of wire from your tranny to lights that are on the ass of your truck. you don't need to run the lights off the circuit that's already there you'll probably continually blow fuses if your try adding those lights on like that. I'd add a relay and grab a constant 12vt from a better line, so that way when your reverse lights on your truck turn on 12 vlts runs to the new relay you added, from there the relay switches on and grabs 12vlts from the new "better" constant that you ran which will then power the lights. that way no ugly switches on your dash and no worry, just pop her in reverse and you're set. just an idea though.