Opinion on universal wiring harness

In that case I'd say read up on the factory system and then fix what needs fixing.
I say this because the kits are not always following the program. Fine if you want or need to change the strategy, but otherwise its just making things complicated.

Splice in and/or replace terminals and wiring where needed.
The good open barel crimpers are pricey, such as the Packard ones and copies.
Perhaps the cheapest ones that might be decent are the IWISS 2412M.
I haven't tried them yet, but will be trying out their 2820 for some smaller terminals that kicked my butt the last couple days.

Sources for Chrysler type wire terminals
Not all of the terminals are easy to find or figure out. So that can be a challenging puzzle at times.

I say read up because i don't know what your background is. If you've worked on generator equiped jeeps will be a world of difference than say SAABs etc. etc.
At the risk of providing background that you already know.
The car has two power sources, alternator and battery. In these cars, the factory wired them together at the main splice. This main splice is where all of the other circuits are tied in except the starter motor. Whether the alternator is providing power or the battery is providing power, the power goes to the main splice and then wherever needed.

View attachment 1715557266

The gage Chrysler labeled 'alternator' is an ammeter. Why is labeled alternator I don't know. But if you notice the car is running on battery all the time, then the alternator isn't working. So in a way it is an alternator gage. LOL

On a 70 and 71, the main circuit and ignition is like this
View attachment 1715557264

In your car, we don't know why the electrics were modified/hacked/altered That's probably the first thing to figure out.
Was there a modification for some new fangled accessory (electronic ignition, stereo, whatever) or
was it because there was a problem?
Or one resulted in the other leading to revisit...

The connectors at the firewall and at the steering column are often sources of problems.

Factory service manuals have pretty complete diagrams and sometimes additional illustrations showing cable routing or circuit diagrams.
Sometimes they left it to the techs to draw their own...

Lots of good info here ranging from how the turn signals work to how to read the diagrams.
Master Technician Service Conference - Chrysler's Training for Mechanics

mymopar.com has some of the same but in pdf, along with some digitized factory service manuals.
My backround is in GM mostly so this is my first mopar. Concering the ignition and engine wiring the PO had setup a custom pertronix hei system, having seen it in other applications i had found it pretty neat at the time but as soon as my ignition started acting up and dying randomly at idle i gutted it and installed an msd setup (didnt feel like trying to learn how the conversion was done), so im all ready pretty familiar with the ignition system wiring never had a starting/idling issue after that. Where im foggy is the wiring for the headlights i find that they flicker and randomly loose light, Other issue i have is that the underdash wiring is just a straight hackjob and a mess. Modern radio was installed that im replacing and when i had got the car there was no gauge bezel just abunch of individual little gauge pods spliced and wired in. Im doing the full harness replacement becuase ive got some nice gauges coming in the mail, a updated reproduction bluetooth radio, and i plan of re installing the AC/ heating system that the previous owner pulled. I really appreciate all the help. I bought a 1970 service manual today and will keep touching back to that for refrence.