Here are a couple choices.
If it were my car, I would strip out all the wire and start from scratch.
If you are not sure of your abilities, find a friend that has done it before.
Take a look at the cars at the track. The simplest way is to buy a complete harness and follow the instructions. Take your time as you only want to do it once.
Decide if you want one or two batteries and where the cutoff switch will be.
Plan it out and you'll have fewer problems.
Try painless wiring or some of the other specialty shops.
American Auto Wire. They can be reached at (800) 482-WIRE.
http://performance.alternatefuelsrac.../painless.html
Hope this helps.