I have a suggestion if you want/need to rewire your GMC headlights - it's not a plug and play project but this will give you a much brighter lights that your truck came from the factory with. First we ALL HERE need to know what is wrong with your wiring harness - if the front wiring to your the lights are good I would pick a spot between your floor dimmer switch and the good existing headlight harness and install a HEADLIGHT RELAY that provides full voltage to the bulbs. Factory systems run all your voltage current thru the headlight switch on the dash to power your lights - if your upgrade your bulbs to any thing other than original sealed beams you stress the contacts in the little switch. Be much easier upgrading your existing harness that getting an all ready cluster mess not designed for the GMC.
