Wire harnesses. When did the design change?

I sold a 65 Valiant convertible to a guy and will be helping him get it running. I got it in pieces so I am not all that familiar with how different it is from the 67 and later A bodies...of which I am much more familiar. The buyer is less experienced than me and is looking to me to steer the course.
I had a 65 Dart and didn't do much work on it to learn but I did notice that the bulkhead connector had only 2 plugs to it compared to 3 like the later A body cars had. The Dart also had 2...

Wire harnesses. When did the design change?
Author: Kern Dog