2 speed wiper motor questions

1970 Dodge Dart. Attached to my 2 speed wiper motor is what looks like a ceramic ballast resistor. Does someone know the function of this thing? My 3 and variable speed motors never had anything like this. I don't see this at all in the FSM service manual wiring diagram.

There seem to be lots of options as far as replacing the motor. Is one better then another? Prices seem to range from $50 to $95.