I know this has been covered many times and written up really well here:
https://www.fsjnetwork.com/forum/viewtopic.php?t=5534
I did this conversion a couple weeks ago and just thought I would add my finding in case it can help anyone else.
I did have to enlarge the hole to 1 1/8”.
I didn’t have to cut anything out from inside my tailgate to make the motor fit.
I used heavy duty pipe hanging strap to secure the motor.
I found that the rear wiper from an XJ is almost the identical shape as the original GW wiper arm. This allowed me to use a 13” wiper blade and the wiper arm came with the nut cover which I couldn’t find for the Durango wiper arm. The original GW wiper arm is in my hand.
Here is the wiper arm I purchased. I didn’t put a link in because they often go dead. This wiper arm comes with the sprayer attached, which easily unsnaps. If I ever do body work on this I think would be a clean upgrade to move the sprayer to the wiper arm and close the hole next to the tailgate window.
Here is a video of the new wiper in action. The noise at the end is just the dry wiper skipping on the dry window:
https://youtu.be/2lYaC69aJuY