I have a set of 37's in the garage. Their resting width at the mounting surface is about 7.5" I checked a set of 37x12.50 nitto's at the dealership while I was picking up some parts, and they were a full inch wider at the bead..
Wow, guess they and you know more than the tire manufacturer, Milestar and pretty much every other company that makes 315/70/17s or 35 12.5 17s has the minimum rim width as 8” or 8.5”. Surprised discount tire would endorse mounting that size tire on an unapproved rim size.
I have these same ones on my overland. I love them so far. Quiet on the road. Great traction in sand aired down to 20. Able to go uphill with rocks and had no issues. I would buy these again when the time comes.