[hatzie]

Originally Posted by zosoppp

If you need a trailer connection I suggest this type, no cutting/splicing required (for 67-72 specifically):
Not certain if it's a match for squarebody era connectors, but there's probably something similar.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

X2 on those Hopkins trailer plug-in units.

The 84-91 CK/RV & 88-02 T400 have Weatherpak plugs back there and Hopkins makes plug-in units for those as well.

I usually expect and find U-haul and Ryder Hitch-Monkey wiring jobs using Scotchloks and open butt splices that have completely destroyed the tail lamp harnesses on any trucks over a few years old.

If your molded plug taillamp harness is badly damaged close to the molded plug you'll find it's not available. You can fab an upgrade to the 1984 and later CK/RV chassis square 2x2 four terminal Weatherpak fairly easily. The four wires are solid colors so all you need is tooling, split poly loom, SXL wire, Weatherpak parts, and the Packard 56 terminals for the bulkhead plug.
The pinouts for those plugs are in the FSM wiring diagrams in my sig.