98 LS1 Swap to 91 C1500 5speed

[Mickeymotormount]

First off, welcome to the site. There are quite a few guys here that have done the swap with a manual trans behind their LS engines. Just use the search thread function to read about those specific swaps with manual trannies. I do recall reading about them here and that there were some specifics that need to be adressed before mating the trans to the engine.

As for your harness, there are different ways to approach the problem. You can either purchase a stand alone harness for your engine which is simply a plug and play deal or you can go the cheaper route (I did) and modify the LS harness to become a stand alone harness. If you choose to modify the harness, check out the site below. It has alot of information on how to do it.

http://lt1swap.com/2000harness.htm

[91ls1silverado]

Thanks for the Reply John. And I am getting a standalone for the ls, but my question is how do i Remove the old harness from the firewall...I can't find a way to get it out of the passengers side...thanks again.

[1991SSP]

I left my stock harness in place on my 94.. I clipped the plugs and taped up the wires off that I was not going to use and tucked them into the wire loom on the original harness.. then I mounted my nelson harness and PCM under the hood, I only ran 3-4 wires off the new harness into the cab.......

[Mickeymotormount]

Good question. I never removed mine since I used some of the wires to power up the modified harness. I would have to think there was a bolt or something in the center of the plug that pulls the mated half of the plug on the inside of the firewall to itself.