Entire 69 dart wiring harness

If you can wire a relay, you can wire a car.
Go buy a cheap bosch relay, get 4 small spools of different colored wire, and an old headlight.
Wire it up on your bench to trigger the light. Add a switch if you want to get fancy.
Then look over the wiring diagram for you car and understand the pathways the power takes. The most complex is probably the neutral start switch, and it's not that hard.
If you can do a switched relay, you can wire these cars no problem. They're nothing more than switches and relays and bulbs.