I'd keep the 3 or 4 main wires for power for the rest of the car (factory has fusible links at the end), coil power, all sensor wires (temp, oil press, etc.), alternator/charge, starter, external lighting, and sending unit if you're using the factory sending unit/wiring (so basically keep most all of it). If you don't plan on using the factory cluster/gauges and want to run new wiring I believe you can scrap all but main wires for power, coil wire (makes for an easy switched 12v source) and the starter wire.