Help with wiper motor & switch

Hey... working through the previous owners wonderful mismatched setup. I finally got everything working, then snapped the clip on the bushing. I haven't pulled it all apart yet, but my guess is that I have a 2 speed crank arm that doesn't work with my 3 speed motor.

Where can I find the wiper motor part number stamped? To clarify, the cylinder motor is a Prestolite ETG 4002 156, but I need to know what that is hooked up to for the crank arm

I want to make sure I am looking for the right crank arm