I used the M&H harnesses ( all 3 of them) in my 67 coronet during its rotisserie restoration I gave it....

You can only purchase them through Year One, at least that was the way it was when I purchased the harnesses appx 8 years ago.. There were 3 additional sub-harnesses Year One did not have and I sent them to M&H ( after a phone conversation with them) who built new ones for me based on the old harnesses I sent them.. The sub-harnesses were all small one or two wire affairs...

They were not cheap, but you can wait for a 20 or 30% off day event ( at Year One) and save quite a bit of money...

The harnesses were a plug and play and have NEVER given me a problem in the 5400 miles and 7 years of enjoyment I have had driving the car... One of the best purchases I made..

A few years before I got my Coronet on the road, I was at the stereo shop and a black 67 chevelle came in from a fresh resto.. The car was quite beautiful.. Owner told me on its first test drive smoke started pouring from under the hood with the smell of an "electrical fire".. Fortunately the battery cables were not tight on the battery and he pulled over, pulled them off and used his fire extinguisher to put it out..
Pretty bad day to have your car burn down from an electrical fire using a 40-50 year old wiring that came in the car..