Heater Motor blower resistor

Does anyone know where I can find a replacement heater motor resistor?
The part number on the one I have now is: 3502736 173
It is in a 73 Duster which had A/C.

Also, is there a way to check to see if it is a working resistor or not?
(Mine only works on one speed and I know in the past, when my earlier Duster did this, it was the resistor.)

Is there an after market resistor or 'fix' for these? Seems I can't find one anywhere.

A little help will be most greatly appreciated.
Greg...................mtn_jake :violent1: