Last winter I found out the most southerly Les Schwab store (on my route going south on 95) was in Fallon, NV. Looking at the store locator shows California having Les Schwab stores as far south as Bakersfield... in Utah as far south as Provo and Price (SE of Provo). There are no Les Schwab stores in Arizona and Wyoming.
Today I took the Marquis to a friend's truck shop. We measured clearances around my steering tires (295/80R22.5) with the air dumped, and again measured clearances at ride height with the wheels full stopped both right and left. The narrowest clearance we could see was about 3 inches. So we tried on a pair of 315/80R22.5 that were already mounted on identical rims to mine. They both looked good and the clearances appeared almost as good as the 295s. I ordered a pair of new Dunlop 315/80R22.5 tires. These tires go to a 9,090 pound weight limit at 130 psi. Plus, we found out the steering rims on my Marquis are 22.5 x 9 which surprised us. We expected the rims to be 22.5 x 8.25 which would mean the rim would have a lower limited max psi due to the narrower rim design and thus the new tires' weight limit could not be fully utilized.
It all seems to be working for me... except for the $609 per tire cost. But these Dunlop 315s versus Michelin 295 XCoach tires will handle the weight better (9,090 versus 8,270 pounds) and cost about $265 less each.