I believe there are 2 companies we have found to be very good, American Autowire and M & H Electric.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
A Fellow FGF'er who doesn't get on this forum much and doesn't post near enough has an excellent web site and did his '68 bird with American Auto Wire. See http://www3.telus.net/public/68bird/wiring.htm
I am going to weigh in for the M&H side. While I will concede that the AAW kit was tempting, I went with M&H and had no issues at all. All the harnesses were great reproductions of the originals, with all the connectors already installed. So the crimper and the soldering iron stayed in the drawer. I figure that they both would have ended up costing the same at the chiropractor (if you're over a certain age ), so I went with the plug and play.
I just spoke to a sales rep at Performance years about a new harness. They sell the both the M&H and American Autowire harnesses interchangeably. He says that the American Autowire guy split off from the M&H guy and they're basically selling the same harness. I asked about having to crimp and solder things and he said they are both plug and play..ready to go. If that's the case, I guess it would be hard to go wrong either way.
If you have the gauge package, go with the M&H kit. It has the heavy wire for the ampmeter. A representative from AAW spoke at one of our club meetings and stated that they no longer do this because of liability issues. You might want to investigate this more......John