I have a 67 GTA convertible with factory (Marti verified) tilt wheel, convenience control and A/C options. The car has been tinkered with over the years, so I can't claim that it has the original wiring or lights, but the wiring appears to be original because of the tags on it. The car was built Dec 1, 1966 in Dearborn.
I took the wiring out of the car last winter, and put it all in the same box. I didn't know about the proof wire at the time.
It had the back lit blue and red warning lights.
It has the early vacuum splitter under the dash for the tilt.
It has the early vacuum can inside the engine bay under the hood hinge.
For the proof wire, or at least what I believe is the proof wire, there is a single black wire leading from the firewall to the relay along the driver side. It is integrated (taped) into the wiring harness part way and appears to have been built that way. It has a male end at the firewall and a ring at the relay. I can't find a triple female connector for it. The wire does have a p/n on it, but it isn't what was identified above (I think it was like 9A611?) I will verify tonight.
Now, I'm adding Speed Control to the car, so there is another dimension of mystery and craziness. In the Speed control section of the MPC , the wire C7ZB 9C877-A is identified as the 'Wire Assy. - Speed Control Extension'. So, if the wire has a triple female end, then it appears that the Speed control and the convenience could both plug into it?
I am adding the Curtis Wright system because my car is an early model and would have received it before the Perfect Circle system was available. I picked up some Speed Control wiring from a 67 passenger Ford and it as a red wire that I had identified as the 9C877 wire. The control unit on full size cars is mounted on the inside of the driver side wheel well, so the wire lengths are off, but it has all the wiring and fittings for the Speed control. I thought I would just adjust the wiring lengths to fit the Mustang.