There was a factory electric wiper motor available for the task force trucks. I know the 56 is different from the 58/59, so like many other differences, the 55.2-57 were likely one way and the 58-59 another. The 56, what I have, has a little mechanical cable that runs from the knob to the switch on the motor assembly and the later ones have a remote electrical switch, IIRC. Both systems show up from time to time on eBay.
