Just sharing what I could readily put my hands on (not that it solves your wheel pulling problem, but it does show that the early 726 has plates holding the axle bushings in:
From top to bottom:
671 with direct single worm drive
726 with direct single worm drive
I'm also with @harmonyards stating that from what we can see in the pictures, this doesn't warrant the gear replacement work you suggested. I would clean it, lube it, and send it.