You'll want 10.50s on stock wheels for the least amount of interference. You'll need to trim the plastic quite a bit, and you'llalso need to trim the lower edge of the fender and the pinch seam. A grinder with a cutoff wheel works well for this. Find the lower bolt that holds the fender to the pinch seam, go about 1/4 - 1/2" ahead of it and cut away. This sounds funny, but once you've cut away the fender and the seam, smooth it with a BFH so no sharp, tire cutting edges are exposed.

If you live in Mesa, you can stop by some early evening and I can show you what to remove, and you can look at how it's done on either of my trucks.