Dennis,
If all your problems involve lighting, bear in mind that the emergency flasher switch is involved in all the lighting circuits. And it is well known to go bad and truly screw things up. A birds nest of wiring is attached to it so if you want to remove it and check it out, be very sure you get all the wire colors written down correctly. Likewise, the grounding issue on our cars can cause a bunch of weird, intermitent problems. I would surely attack all the ground connections and the flasher before going to a new wiring harness endeavor.
Larry
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.