The harness for the three bulbs or the main feed down the rocker to them?
Check out Pete Disher's Coralsnake site. Sells most of the Alloy Metal stuff, good guy to deal with. Shelby specialist, but knows these cars too...
http://www.thecoralsnake.com/wiringlist
Be careful on the light harnesses and many do not have OEM style fittings. I have a useless spare sold as "correct", but.... the ones I finally got, I think from Pete, have the correct press in sockets, but did need a inner "circlip" pressed on (provided with the wiring) to firmly hold the sockets in the taillight bucket...