There is a hole in the firewall for passing the wiring harness to the engine area. If you are going the donor route, you should have saved the large rubber grommet from the donor.

I went with a carb build and ran the harness down the passenger side of the tunnel, through a 3/4" sq. tube at the front edge of the trunk and under the trunk aluminum.

Basically, lay it out with out fastening anything down and move it around until it makes sense to you.

Ray

 

Are the rear harnes wires above or below the trunk aluminum for wiring the tail lights.

The tail light wiring can be connected outside the trunk aluminum, except you will have to route a couple of wires into the trunk for the license plate light and ground. I connected all my lighting wiring using weather pack connectors. It makes it much eaiser to test circuits and re configure the pins in the connector, instead of cutting and splicing if you make a mistake. John

 

Ray, the pass through was originally on top of the passenger footbox. Anyone have a picture of it coming through the firewall?

 

On mine, a MK-I.5, there was a hole in the firewall and the computer harness went through another hole in top of the passenger foot-box.

Ray

 

Al,

I have a MK III that was designed for the computer harness bundle to go through the firewall right near the windshield bar on the passenger side. The computer was then specified to be mounted inside the passenger footbox on the outboard wall. The problem with this is that the wire bundle comes in through the firewall and wraps over the 2x2 tube below the dash. In the finished car you end up with this big wire loom near the passenger's right knee. I skipped this idea and put my harness bundle through the footbox lid, just like the MK IIs.

 

Below are a few pictures of how I ran my wiring to the back of the car. It is a 4.6 build but hopefully you can get some ideas from them. The first picture shows the wiring thru the firewall on the bottom left of the picture. I did change the location of my battery cut off switch from the trunk to the back of the tunnel.

 

One more.

 

Thanks...helped a lot