Re-Wiring 1975 Plymouth Duster

What’s under the hood? With that scoop I doubt it’s a slant 6 or a 2bbl 318?

Buying a downloadable manual will be worth it in the long run. You’ll refer to it a lot to fix the existing wiring problems and it will be the proper road map instead of using generic ones. The later year A bodies have extra safety/gizmos that are not in the earlier more available manuals. At least they got rid of the seat belt safety interlock in ‘75 (it was a 1 year only item for ‘74) as it caused a lot of problems.