We replaced our 12R-22.5 with the 315/80r-22.5 Michelin XZA2 Energy tires.
Superior Tire in Salem Oregon did the work and I purchased the tires through the FMCA Michelin program.
We have driven about 6,000 miles with the new tires on all sorts of roads from freeways to rutted dirt Mexican roads and we have had no issues so far.
I did ask about the extra width and Superior was not concerned about it. I looked between the tires and there is lots of daylight.
Former owner of a 1969 F600 Skoolie.
1998 Ford B700 Thomas body 65 passenger. 5.9 Cummins 12 valve with MT643 Transmission 123,000 miles.