Wiper Switch Problem

I have a 1973 Duster. When I got the car the wipers didn't work. The lot that I bought it from changed the motor and said that they worked. I took their word that they worked and didn't find out until later that the wipers didn't work. Any way, my guy said the switch was bad so I found a used one. He pulled the switch out this afternoon and it wasn't the switch I have. It's a switch with variable speed where as the one I bought is for a 2 speed motor. The motor is a 2 speed motor. The switch in the car is for a 1970 and '71. Does anyone have any logical idea why I would have an old style switch in my car?