In the 6th post you can see where the PO cut and spliced the newer head unit connector into the old harness.
So I would say the old connectors are long gone.
I would be looking at the wire colors on the cab side of that bunch of butt splices.
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.