StepsideStroker

I am swapping an 02 Vortec 5.3 and 4L60E into my 91 Silverado. I got the complete motor and tranny, wiring harness, underhood fuse box, and everything else you can think of.
I will be splicing into the pigtail's coming out of the underhood fuse box toward the firewall to integrate it into my factory harness. Does anyone have the schematics that show these wires from the UFB to the cab?

Can anyone tell me on the passenger side behind the glove box, there is a doubled up connector (clear in color) coming from engine compartment that plugs into a black connector in the dash harness. What is this connection for? A/C connections maybe?
The 12ga red power wire that comes in from the same loom coming from the power dist. block on pass side firewall goes to what? I don't think it's fuse box power, there's already one running outside firewall to the through firewall fusebox connector. Blower motor possibly?

I've got most of it narrowed down pretty quickly last night, but I'm just not sure about these wires. I'd like to have everything go in on drivers side and close the holes in pass side firewall altogether, but don't know if these are needed or not.

Thanks for your help.

LS1GMCTruck

iTrader: (2)

Although my '96 wiring is totally different than your '91, I believe the large red & black wires that you mentioned coming out of the passenger side firewall are for the blower mainly, and also your HVAC(heating, venting, air-conditioning) controls. On my '96, there was alot more computer related wiring that tied into the trucks dash controls than you should have...But I found that a lot of the ground wires(blacks or black with white tracers) traced back to, and relied on the couple of large black grounds that went into the passenger/blower side of the engine compartment. The '88 through '98 truck bodys were the same, but the '96, '97 & '98 were completely different than all the other years as far as wiring, engines, controls, etc... In other words, I can't help you with your specific wiring questions & I don't think anyone else will be able to, either, unless they have direct working knowledge of your specific year pick-up. What your best help will come from, is a year/model specific Chevrolet or GMC Service Manual, that can be bought on E-Bay at a very reasonable cost. It includes all the wiring colors & codes & functions and answers every other question you might have on the entire truck. Hope this helps. Gar