I played around with this a few months ago.
My first attempt was to get a momentary pushbutton switch from radio shack, drill a hole in switch housing, and hook up to brown and brown yellow wires in switchmaster connnector AN/4.
The conector is tie wraped under inst. cluster. I belive it is rectancluar with four wires,brown, br/yellow, yellow, gr/red.
Brown wire is ground.
Brown/yellow cycles functions.
yellow and gr/red increments trip 2 up and down.
I found a small switch @ radio shack PN 275-1571 that looks like you could get all three to fit.
So far I only have the one switch installed to cycle functions. I haven't tried to fill the hole I made for big switch and install the small ones.
I'll probally just mount 2 more switches in dash next to spedo.