Jim honestly, that is the worst rats nest of wiring I have ever seen and I have seen some bad ones. You are better off to strip it all out and start over. It is really not that hard to re-wire. It would be much easier to do that than to fight that mess. Just think what a mess it would be to break down on the trail and have to deal with that. I could probably give you instruction on the re-wire.
Just leave all wires running through the firewall. Detach all wires out front and take off all that plastic wire protection. Do not cut anything coming through the firewall.