I read a post by notamos in another thread saying that Polaris uses wheel studs the same size as XJ backing plate studs. Sure enough, they do. I found that Polaris part no. 7518378 wheel studs are a very close match for the backing plate studs that came off of my 8.25 axle, but are 3/8” longer. They also seem to be a tiny bit (3/128”) bigger around the knurled part of the shank. Of course, that little difference could just be attributable to the knurls on the XJ studs having been flattened somewhat when pressed into the mounting flange.
Anyway, I hope someone finds this information useful one day.
I probably ought to add that my research shows 50 foot pounds is generally accepted as the max torque for a 3/8-24 grade 8 bolt. So that’s what I’m going with.
Update:
I couldn’t press the Polaris studs into the holes. I just didn’t have a decent mechanical press that would work in the limited space available and couldn’t quite get them fully inserted using a nut to draw them in. So I reamed out the holes from 3/8 to 25/64. Worked like a charm. Studs went in, but are nice and snug.