The current polarity reversing switch was an electrical device mounted on top of the starter motor casing. It has three terminals. A slotted rod connects the lever actuating the starter motor to the current polarity reversing switch.
Wiring the switch is not difficult, but I don't have any diagram handy, and I don't remember the source and end of the wiring for the switch. I know the purpose was to change the polarity of the current going to the distributor, ostensibly to reduce the wear on the points in the distributor.
If you have a mechanical shift starter motor (that's one with a boot stomper on the floor by the foot feed), then you could satisfy your craving for a polarity reversing switch. On the other hand, the old truck do just fine without the dang thing.
