M&H Electrical Fabricators
Typically they do not deal direct, you must go through a dealer. At one time Year One was the only one but recent I have seen them being sold by others.
They will deal direct on non catalog items like C-Body or some secondary harnesses.
About 2013 I had them do the harnesses for a 1969 Dodge Polara, had them in a few months.
Recently I had them do basically the same harnesses and it took them a year.
You should be able to get most A-Body harnesses from Year One.
Alan