1964 dodge dart wiper switch

The FSM wiring schematic details all colors and wire gages. Indeed, I just saw a schematic for your year in another post (early A forum). I have at least three 64 & 65 wiper switches and none have that white plastic box on the rear. Perhaps that is for a "washer" function. The black square bulge on the rear looks like what is on variable-speed switches, but Google Images is smarter than me.