American Auto Wire Install??

If at all possible, get yourself a sheet or to of 4X8 plywood, and put your stock harness on it, and build your new harness side by side with the old. Upgrade your wire gauge and connectors next to it. Just my opinion, but I wired 747's for over 22 years using this method. It's working on my 70 Swinger 340, with bigger wires, and the mods needed for a modern car. Just my .02.