Frank, depending on the application, you would need 10-12 gauge for the high amp stuff and 14-16 for the medium amp stuff and 16-18 gauge for the low amp stuff. The important thing is to use relays where required and fuse everything with the correct amp fuse.

If you under dash wiring is shot, the rest of the car’s wiring may need attention too. Why not in think of using a complete Painless Wiring (or other brand) complete harness. All the wires are clearly marked and color coded. You can buy as many circuits as you require and add to them at any time too. I think you’d be happy with the result and the investment.

There are also many good publications avalable for wiring cars. One is called Hot Rod Wiring and it’s very useful for kit car applications.

I got my Hot Rod Wiring book from Speedway Motors (Lincoln, NE). http://www.speedwaymotors.com

I just did a search (hot rod wiring) on http://www.Amazon.com. The book I have, ‘Hot Rod Wiring’ and another that looks interesting, ‘How to do Electrical Systems: Most Everything About Auto Electrics’ came up.

I have a 1985 Mustang SCCA American Sedan Class road racer that has only brake lights, wipers, electric fuel pump, MSD iginition and the starter/alternator/battery. The builder wired the car himself and it’s scary to say the least. I plan to re-wire it in the future to include headlights and taillights so I can drive it to cruises and track events. I will probably buy a basic harness from Painless Wiring or another harness vendor to accomplish that.