I installed a Painless " Universal Truck " harness I picked up on E Bay. It had good instructions and diagrams, based on the GM wiring colours. You choose where you want the fuse panel. The harness is divided into sections for front, rear, and cab wiring. I had never done any serious wiring before, but once you get going and take your time it worked out great. When I got stuck, Painless had a great customer service department to talk with. My harness has ( 18 ) circuits which allows extras like Air Conditioning, Windows / Locks, Elec. Fuel Pump, 3rd Brake light, etc. etc.
