73 240Z Wiring

Actually, IMHO, Wade was not far off the mark. The OP stated in his initial post that he didn't understand much of what he was doing and that he was looking for a shortcut.

I try to minimize jury-rigging wiring in the car. The modifications I make tend to be things like adding relays to the headlight circuit or bypassing the obnoxious seatbelt interlock relay. I wasn't going to offer any advice myself, but when the OP asked about an engine harness, I directed him to a potential & reputable source.

I will try to help people with electrical issues online and on the phone. However, I would agree with Wade that if you have little knowledge of automotive electrical systems and want to ignore all of the work the Nissan engineers did during the design & production of the car, it would be best to seek the services of a professional.