I used the harnesses from @pgamboaand the process was super easy. He has videos that explain how to do the whole process. Removed door cars, swapped harnesses, and mounted the new mirrors. The mirrors I got had an option for a 4th stud which I did as another way to keep them from vibrating.
Just finished my upgrade from DL3 mirrors to tow mirrors and they look and function great. @pgamboa was a big help during the process. Now I have a set of DL3 mirrors with harnesses hanging around if anyone is interested.