Update:
While the harness on that Chevy Duty signal switch was a match, the signal mechanism and cam were not a match for my column.
I'd seen these same factory deluxe columns on old 60-61 bel-airs/biscaynes, so I gave a Sinclair's signal switch for one of these a try. The mechanism was a match, except for the horn wire which I had to provide for.
I think what may have happened was the Deluxe wheel was borrowed from a donor, probably a biscayne or such, and along with it the signal mechanism, lever and signal mechanism housing.
Lesson learned...
