Try the truck tire places - they sell and install tires in the size you need. Camping World does also. Get quotes from several, including any fees, mounting and balancing (what they call the "out the door' price. Also ask about getting a credit for the old tires, which are regroovable and often re-sold to truckers.
Michelins seem to be the tire of choice among American Coach owners now, but they are the most expensive tire by far. The Goodyears suffer from "riverwear", a pronounced wear along the outer edge of the front tires. Generally, though, this does not cause a problem before the tire wears out from age or miles. Some AC owners have complained about badly out of round Goodyear G670's. A severely out of round tire is difficult to balance properly. Other choices popular are Bridgestones, Yokohomas and Toyos.