"GHOST1750"...Take a look at the Hankook AH12 RV tires. You won't go wrong with them and if you do a search, you'll find no complaints. I replaced my Goodyears on my Diplomat with the Hankooks and they rode smoother and handled better. You can usually find the AH12's for about $400.00 each.
The only problem with the Hankooks (a marketing blunder since everyone loves them) is that they don't come in all sizes. In your case, they come in a 255/70-22.5, not the 255/80 that you have. Theoretically, they would be a little shorter and a little wider, but since all companies fudge some on the specs, I would compare them to the Michellins, my guess they would be pretty close to identical.