Even if you do a rewire one at a time, you are going to want to install fuses which are not original to the truck, but improves safety tremendously and is a must do in my opinion. In my case I added in line fuses which you can do, by it looks out of place. A fuse box under the dash or mounted on the firewall (for easier wiring) would tidy it up. although I have never used a universal wiring harness, I understand that every wire is labeled as to where it goes so it should not be such a headache.
One if our fellow ‘bolters ”bartamos”, is an expert in installing these kits and has posted in this thread. I’m sure he can give you the lowdown on the installation.