Paul,

Red IDed it.

My 54/55 GMC 2-ton COE has that type of adapter for the speedometer and two-speed rear-end. I think that Jim Carter sells a 9-foot-long cable with the wider end-cap needed for that switch (I hope it works).

I do not know how the 2-speed selector-switch attaches to the speedometer adapter but I will be dealing with it this summer as I put the painted COE sheet-metal back on top of the engine. Spanky will be my savior.