I've been a tech for 12 years and I consider electrical stuff a strong point, so re-working a harness is no big deal, just time consuming. I've reworked a few harness for other swaps and I always keep harness from the cars I part out to have extra wiring, fuse boxes, etc around. I have totes crammed full of harnesses lol. The harness I used came with a 6.0 I bought so I expected it to be a 6.0/4L80e harness. I guess it didn't come with that engine originally because it was a 5 speed harness. Luckily the guy that sold me the trans cut the connectors off and left them on the trans, so I had to add a bunch of wires to all those connectors. I removed all wiring that I wouldn't need. Used a fuse/relay box from a 4th gen f body. I didn't get a pic of the biggest mess of wiring I had with the harness laid out and 2 totes worth of wiring laying around too lol, but here it was apart
Everything soldered together, plug in the right spots and taped up
And all covered up with some split loom
Installed the harness. I used the stock engine harness body/fuse box connector. I used the starter wire to control the starter relay. And the keyed hot coil wire to control a relay that powers the fuses I wanted keyed power on. The temp gauge wire is connected to a stock 98 Camaro temp sender. All other wires I needed in the cab pass through a hole above that connector. I ran wires from the pcm into the cab for speedo, tach, ac request, and cruise so that I can use all of those later.
I built the harness so that I can hide the pcm inside the passenger fender and the fuse box will be mounted to the fender next to the battery
I've got 100' rolls of 2 sizes of double wall, adhesive lined shrink tube I bought on ebay. Much better than the stuff you can usually find locally. It shrinks 3:1 rather than 2:1 like cheaper stuff, and the adhesive lining makes it water proof which is nice under the hood.
