Hemibeep is correct. You need the three speed wiper motor, the plastic cam/arm for it, the in-dash three speed wiper switch (also not the easiest or cheapest pice to find) to control it. I’d look at the wiring schematic too. I may require different under hood wiring but I am not certain on that. I’ve never converted.
As a thought, I think, but am not sure, that the interference from the 2 speed wiper motor hitting the base of the air grabber air cleaner isn’t a lot and some people have notched it out the base and modified that too. Again not sure, but maybe that’s a possibility for you depending on how correct you want it.