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After almost three years of searching and looking at a lot of cars, yesterday a 1991, 4-cyl, automatic Mustang coupe came home with me. It's a roller without the engine. My plan is LS3 power (480hp) and some form of the T56 6-speed. Only manual transmissions for me!
Even though I've lurked in this conversion forum for years, I've still got some very basic questions.
1. Wiring harness. Do I really need to be concerned with the OEM harness in the car? The previous owner did some cutting and splicing. I'm not happy with it.
2. Since I'm going LS, I would think that the OEM Ford harness is useless but what do I know? I'm sure I'd still need the parts that deal with head and tail lights but as far as engine management goes, I wouldn't need any of that right?
3. What if I want to keep the stock Ford instrument cluster? How do I tie in the LS wiring to the cluster?
4. How did you wire your LS Fox?
I'm not even sure that I'm asking these questions properly but at least this is a start. On the road from San Antonio to north Houston Finally in my driveway!
The wiring harness that runs on the passenger side is for the engine control and can be removed. The wiring harness on the driver side mostly runs the car and should be retained.
The stock dashboard can be made to work. I installed the ford senders into my lq4 using brass npt to metric adapters. Everything works except for the speedometer because it is mechanically driven. There are solutions to that but I haven't gotten to it.
I kept the wiring on the driver side and ran my new ls harness on the passenger side. I installed a goldbox where the factory ecu was and used the same hole to run the wires thru the firewall.
Awesome information, markster. Earlier I was researching this wiring and you confirmed what I had found! I'll focus on salvaging the left side wiring and I'll just remove the right side wiring.
The car appears to be in great shape but after I washed the car, I noticed some shoddy looking body work on the driver's side rear quarter panel in front of the wheel . Even though the paint job is fairly new, it's not what I'd call good. My plan always was to have the car repainted because I want it to look really good. I've still got two more days with the U-haul trailer so tomorrow the car is going to at least one paint and body shop. I spoke with one on the phone and I'll be there with the car in the morning.
I'd really like to do more of the mechanical work before the car is painted but I'd like to know what kind of money I'm looking at to have a nice paint job. I was thinking of having the car sprayed next spring or summer after I've had a chance to do mechanical work on it.
You’ll find the engine compartment is really roomy compared to your WS6, no cowl ledge or hideously oversized shock towers to get in the way. A trend for Foxbodies is an SN95 complete dash if you’re up to that (YouTube) The trans tunnel is on the small side. Using a Foxbody 5.0 or LX v8 car 8.8 will give you the best tire/wheel options, everyone wants to use an SN95 in the Fox but it adds .75” to each side and messes with your sizing and backspacing. Assuming your going 5 lug if it doesn’t already.
You’ll find the engine compartment is really roomy compared to your WS6, no cowl ledge or hideously oversized shock towers to get in the way. A trend for Foxbodies is an SN95 complete dash if you’re up to that (YouTube) The trans tunnel is on the small side. Using a Foxbody 5.0 or LX v8 car 8.8 will give you the best tire/wheel options, everyone wants to use an SN95 in the Fox but it adds .75” to each side and messes with your sizing and backspacing. Assuming your going 5 lug if it doesn’t already.
I've still got my rusted out 1991 Mustang GT that I've owned since it was brand new. Salt water air did a number on it when I lived near the beach in north Florida! This GT is going to donate many of it's parts to the "new" coupe.
I did the 5-lug, 4-wheel Cobra disc brake swap to the GT about 10 years ago. All of those parts and the 8.8 GT rear end are going into the coupe.
My rusted GT has a very nice black interior and that will all go into the coupe as well!
Since I started this thread asking about wiring harnesses, I guess I can always cannibalize any needed harnesses out of my rusted GT.
12-02-2018, 10:07 PM
Fox body conversion wiring harness questions. 
. Even though the paint job is fairly new, it's not what I'd call good. My plan always was to have the car repainted because I want it to look really good. I've still got two more days with the U-haul trailer so tomorrow the car is going to at least one paint and body shop. I spoke with one on the phone and I'll be there with the car in the morning.