You won't be working on all...
You won't be working on all of your wiring directly on the chassis, so have a workbench with plenty of room available. Better yet, use a folding card table that you can set up right next to your project so you'll have plenty of room for spools of convolute, harness tape, tie-wraps, and more.
If you've been following our online Web diary, you've likely seen several weeks of diary entries where we mentioned various sections of the wiring portion of our project. Wiring can be a daunting task for even seasoned automotive wrench turners. There's a big difference between bolting on a brake caliper and determining the proper gauge of wiring to use for an alternator circuit. Having the proper circuit protection, gauge of wiring, and harness routing is imperative to a safely wired project that will not give you problems down the road.
Be prepared to spend a fair amount of time in the wiring phase as much of the installation locations for the electrical items (starter solenoid, fuse box, gauges, and so on) are your decision, and you must factor in functionality, wire length, and future access before drilling a single hole. There were times when we literally stood staring at the frame with a part in hand for half an hour, trying to determine where it would fit best.
The Factory Five Racing Roadster kit is designed to use the original wiring harness and circuits/switches from a late-model Mustang. This was fine back in the late '90s when these Mustangs weren't that old, but now you're easily looking at 15-year-old wiring with brittle connectors-not to mention there's a lot of wiring on these donor harnesses that you won't use (such as power windows, power locks, and airbag). The newer the donor Mustang, the less this is a problem, although there will be more wiring to deal with.
A much cleaner alternative is an aftermarket wiring harness. FFR sells one for those using a carburetor instead of fuel injection on their cars. Since we are not using any donor parts, we had FFR send us its carb-wiring kit along with our project. Between the FFR harness and the EFI harness that came with our Mass-Flo EFI system, 100 percent of the car's wiring is new, with the proper wiring size and connectors ready to go out of the box.
The wiring aspect of the project requires a few specialty tools. You'll want to have a good soldering iron/gun and crimping/cutting pliers to make solid connections. If you intend to use any specialty wiring connectors, then you'll need the proper crimper for those terminals as well. We plan to use MSD Weathertight connectors for any exterior connections (lights, fuel pump, and so on) and MSD Deutsch connectors to make the dash panel removable for future service/repairs. Both of these wiring terminals take their own style of crimper, but MSD offers a crimping tool with replaceable jaws that will work with all sorts of special connectors. A butane hand torch is convenient for heating and sealing shrink-wrap sleeving, and a simple DVOM (digital volt-ohm meter) is a must-have for verifying circuits as you plan and route your wiring.
With our wiring almost complete, we'll be moving on to the body soon, though we still have a few loose ends to tie up from earlier parts of the build.
 As the wiring was laid out,...  As the wiring was laid out, we used a 12-volt source for testing. Once the car is ready for test driving, we'll also need a battery for the charging system. We chose the Optima Red Top 34 battery, PN 8002-002. With 1,000 cranking amps and its spiral-woven, absorbent glass-mat (AGM) design, the Optima does not leak and can be mounted in all sorts of positions. |  The FFR Mark III chassis was...  The FFR Mark III chassis was reconfigured to mount the battery in a plastic battery box within the trunk, whereas the Mk II chassis previously had the battery mounted under the trunk floor. We can understand the ease of service right in the corner of the trunk, but the trunk is pretty small to begin with. We decided to relocate the battery back under the trunk floor with an FFMetal.com mounting kit ($89.99 plus shipping) that has an access panel for the trunk floor. |  As you can see, the Group...  As you can see, the Group 34 Optima fit the FFMetal.com battery box perfectly. Make sure you purchase a battery without side terminals due to the conductivity of an aluminum battery enclosure. |
 Remember what we said earlier...  Remember what we said earlier about deciding on part locations? The starter solenoid is just such a situation. Not only did we have to decide if we wanted it under the hood or closer to the battery, but where to mount it for access. We ultimately decided on this upright behind the driver seat, close to the battery. This way, our long battery cable to the starter will only be "hot" when the key is in "start," which is much safer. |  The FFR-supplied wiring-harness...  The FFR-supplied wiring-harness kit comes in sections. We started with the rear body harness first, which will run up the transmission tunnel to the rear lights, fuel-level sender, fuel pump, and more. Here, we were just starting to separate and route the wires. Lots of inexpensive tie-wraps held everything together as we decided what went where. |  The battery cable was routed...  The battery cable was routed from the starter solenoid at the left rear to the engine's starter at the right front via the transmission tunnel. Insulated mounting clips and 31/416-inch rivets secure the battery cable. The main chassis wiring to the rear was secured via tie-wraps as we determined routing. |