I don't remember what I posted in my swap thread, but you may want to looks there. Thread's called 5.3L LM7 in OBS Silverado (or something like that). I'm terribly sleepy now, and about to shut laptop down. My thread has picks of the underhood fuse block, but dunno about wiring schematics. AllData helped me MORE than Chilton's or Haynes manuals. Cheap investment. I'd have to look at the truck tomorrow to tell ya exactly how my EXTERNAL fuel pump is wired. I will say that I pull 12V power from the battery (point on fuse block), and the signal from the underhood fuse block to. I bypass the OEM relay to and aftermarket relay that came with the pump (ProCharger kit). Found a good ground point, and badda bing, badda boom. Supplied fuel. An internal pump assembly would be better, but an external pump work VERY well. Just don't drain the tank on "E" (which I don't go lower than an 1/8th of a tank).

Good luck!