ground for the "harness"? things have their own grounds, the harness supplies power - the rear lights all get their ground from their mounting to the bed/frame - might need to add a ground wire from the bed to the frame, which should be the general ground for the truck
if your battery is running down just sitting there w/ nothing on, there's a short someplace, and it doesn't hafta be the alternator - disconnect the ground cable from the batt, put your meter between the neg post and the ground cable, and start disconnecting things until the drain disappears to narrow it down
Bill
