Early model Rallye clusters and switches panels from the factory (70-71) were all set up with variable speed switches and late models (72-74) were set up with three speed switches. The two speed switches did not have the ability to drive a pump motor for the washers. The early model variable and the late model three speed did by pushing the knob in that would activate the washer motor. The good news is the main dash harness carries the washer moter wire to the main wiring block. The engine forward harness would continue that wire on position 19 over to the washer motor. There are some position changes that have to occur at the switch connector to change from a two speed to a variable speed. I do have restored variable speed switches that I could help you with, too.
The wiring isn't so much the issue as changing out the two speed motor to a three speed and the linkage swap out from the wiper motor to the wiper arms. Now that is where the work and some dollars would come into play. You may want to contact Kim, a member here at CC.com - Passions for Mopars to inquire about a restored three speed wiper motor. I may be able to help with the linkage change over parts.
I can go into more detail on this if you are interested. You could send me a PM and we can go from there. I hope this was some help. This will not be a quick change over and just want to make you aware of what's involved.
Slotts
