Complete wiring harness for Hotrods or my D-100

Here's the deal. I'm sure someone on here has gone through a similar situation. A 1964 D-100 didn't come with fuses, fusible links, relays or much of anything. No dome door switch, map, backup lights. No neutral safety, horn, radio, but did have a 2 speed heater. Get the picture and setup for my questions. None of the gauges or light switch will be reused. I'll probably retain the wiper and cab dome switch. My eventual plan is modern AC, stereo, gauges, led lighting and maybe cruise control. I'm thinking an 18-21 circuit universal wiring harness. I have an electronics background and I'm pretty good at wiring. It doesn't scare me ripping it all out since I have to anyway. The truck has a mild 440 and 727. Don't hate me but, some of the universal harnesses state they work with GM/Ford and Mopar but, list GM connectors. I plan on using HEI, universal gauges but, the alternator/charging undecided.
Questions: Is there some reason why I should get a Mopar specific harness? Any harness recommendations for a complete rewire? Thanks Craig

I don't know why you need Mopar, other than something like the turn signal switch, and you can cut that off and put something else on there. Some universal harnesses come with such connectors

Also the connectors you need can likely be rebuilt. EG on the A bodies such connectors as ignition swtich, headlight, wipers, dimmer, etc, are all plastic bodies and use what are called "Packard 56" terminals. You can buy them and crimp/ solder to your new universal harness

Just make sure the darn thing has enough wire to reach the tail lights!!!

Another thing, some more modern relay/ power distro boxes can be used to advantage. I bought two Jeep ones, tore them down, and intermixed parts to get more relays in one box.

Here Holley HP injection in the corner, the Jeep relay box, and the fuse panel for the new harness mocked up. (In my Dart I pulled the air vent box out, and subbed a cut down Mustang vent) You can see the butterfly shutter just ahead of the fuse box

I suggest you get an under-dash harness from a 1965. I did that for my 1964 Valiant (65 Fury harness cheap on ebay), to change to the better 1965 bulkhead connector. It has 2 large buss-bar feed-thrus for the large ALT and BAT wires. 1963 was the only other year which did that. In 1966, they added a 3rd connector for the wiper wires (motor moved into engine bay) and moved those wires to normal 57 terminals which like to melt. Ditto for 1964. That will also give you 2 more terminal feed-thrus than 1964. You will need to cut the square hole ~1/8" taller. I am assuming a D100 and Valiant used the same bulkhead. Most dash wires are still sound.

Old engine wires are usually degraded. I rewired all from scratch. Like 67Dart273, I added a fuse/relay box, installed near the battery. I ran small 20 awg ribbon cable from bulkhead to relays (no current needed), which then switch in the power. I used a box from ~95 Jeep. It is narrower than post 3 w/ a lid that swings the other way. I think his is the later version. I recall ~7 relays, plus fuses. I replaced all factory relays on the firewall (starter, horn, ...) and relayed the H/L headlamps, AC clutch, IGN, fuel pump (for fuel injection) and such. If your bulkhead connectors on the engine side are brittle, you might find good ones on an 80's Dodge motor-home. I have seen those use older connectors that often match my 1960's cars. Good luck.

I just re wired my whole car with Ron Francis. A little bit more cash but super easy to plumb in. Great customer service too. Additional items easily added. Have a look.

Gets rid of the dangerous bulkhead connectors too.

No bulkhead on the truck to speak of. 64 uses a rubber grommet with M/F bullet connectors. Good ideas from you guys.

Also I would not necessarily spring for high end stuff like Painless or Francis, although Ron Francis seems to get a lot of good press. One of the member on here likes Americal Autowire. Many people are marketing these with knock off fuse panels.