if you have the 58/9 style, where I think the 2 speed is actually part of the switch, you'd have to find a switch [64-66 2 speed may suit], which could have the knob changed [individual regular knobs available from various vendors] .... changing the knob works fine on the switch supplied w/ the replacement electrics, I've done it .... if you already have an electric, the "replacement for vacuum" won't work with the electric arms, you'd need the one designated for "replacement for original electric"
if you have a 55-57 wiper motor [fits 58/9 that originally had vacuum], the actual switch is part of the wiper motor assembly, the dash knob just controls a cable that moves it, stop, low, high ... I haven't seent the knob/cable as a repro, but a used ones are around
Bill
