Are the Michelin AT2s not available in 18s? When I was looking at tires, I even considered switching to 18" wheels because the 18" E rated tires have 4-500 lbs more load capacity than 17" E rated tires.
I ended up getting the Nitto Terra Grappler, which in 285/70R17E are rated for 3,750 lbs per tire. The Nittos seem fine thus far, but you should have more choices in the 18" sizes than I had in 17s.
My top choices would have been the Goodyear All Terrain Adventure or the Michelin AT2s. Sadly, in the size I wanted, the Michelins are not available in E rated at all, and the Goodyears, while E, were rated for 600 lbs less weight per tire than the Nitto, so I went with the Nitto for extra insurance. If the Goodyear or Michelins are available in a size that you want for your truck, I would strongly recommend them.