Rewiring your classic truck, or any vehicle, can be a daunting task. That spaghetti-like mess of wires can really be overwhelming. Here's a few tricks I have used over the years to rewire projects from scratch.

First, choose an aftermarket harness to install. Quite a few are out there, and they all work well. My personal favorite is one from EZ Wiring. Their 18- or 21-circuit preterminated panels work real well in both trucks and cars. The circuits include those for dome lights, A/C, third brake lights, reverse lights, cruise control, cigar lighter, power windows, power door locks, electric fan, and more. I prefer EZ Wiring kits over the others because the printed names on each wire are just that, the name of what the wire does. Other manufacturers also print the circuit the wire applies to, which can be confusing and hard to read on some smaller-gauged wires. EZ Wiring kits are offered in a GM color-coded format that is easy to get used to. Having done so many over the years, I can sort them out by color and not so much by the words printed on the wires. Though, the names of the wires printed on each one make the wiring job so much simpler. A booklet is also included that has the popular Ford, GM, and Chrysler charging and turn signal circuits drawn out as well as basic light, ignition, and dash circuits. Plus they have some helpful hints listed.

If you are wiring a car that includes a fuel-injected engine and you are using a harness from the injection manufacturer or a kit from suppliers like Street and Performance or Howell, I have found it works well to run all the primary wiring from your fuse panel kit and then install the fuel-injection harness. Laying the fuel-injection harness on the floor and familiarizing yourself with it and where the hot and ignition feeds are in relation to where you need them is a big help. Some kits also have relays and small fuse blocks that need to be mounted as well and with a little preplanning they will integrate right in with the fuse panel mounting and primary looms. Mounting of the computer to be used is probably the hardest part of most kits. They have those so well designed that they really are plug-and-play. Plug in all the sensor wiring on the engine, mount a couple of relays and a fuse panel for the injectors, and hook up a couple of hots and grounds, and you're pretty much done.

The next thing to think about is the mounting of the fuse panel, relays, and additional control units like MSD ignition boxes, electric fan control, and others. In the F-100s I've built over the years, we didn't want any bolts or screws going through the firewall, so I make up a 1x1-inch square tube with brackets on each end to bolt the tube to the sides of a couple of interior braces at the cowl section of the truck directly behind the firewall. This bar also mounts the A/C unit on the passenger side. A panel of aluminum or sheet steel is cut to around 15 by 7 inches and spot-welded or countersunk screwed to the tube. I've even welded T-nuts to the firewall in the mock-up stage and used them to retain a piece of 1/2-inch-thick plywood that itself has T-nuts in to mount the panel and A/C. This can be quite a pain if you want to later add mounting points for something else. For me the 1x1-inch square tube worked the best.