How to identify which Wiper Motor (2 speed or 3 speed) Should be on 75 Duster

1974 was the last year washer manual foot pump was offered. 2 speed wiper switch for 1975 is part #3746851. Go to Ebay .then enter 1975 dodge dart and click on search. Now look on left side of screen under category scroll down to sold items and click there. Then look at original listing and you will see location of washer tank from under hood photo.