If it won't park, you have a ground problem. There is a metal strip on the back side of the switch panel and it has to be grounded to the dash or the motor will not go to park. I've seen it a dozen times. Turn off the switch and take a grounded wire and touch the strip and see if I'm right.

You did change the wiper arm out inside the cowl? The 3-speed arm is totally different thatn the 2-speed arm. The pivot is different as well.