What do I need for a proper under-dash rewire?

Get ahold of a factory service manual, pull the harness out and go through it wire by wire until it is back to factory. Think about your aftermarket accessories (tach, stereo etc) while you are doing it and make provisions for them. An added bonus of doing this is you can troubleshoot easily after because you know exactly what goes where. Grabbing an assortment of Packard 56 connectors is a must. I got mine on Ebay. Also if you have a spare wiring harness from a parts car, they are invaluable for little bits you cant easily source elsewhere.

Cley