Unless you lift it, 285/75 are about as big as you can go w/o rubbing on a 100. 255/85 fare a bit better since they are narrower. I know from experience. Duratracs are great AT tires but suck in mud (they pack up fast and don't shed) and don't do well in snow deeper than 3" I'm on my 3rd set. IMO, very over rated for winter use. In single digits they get hard loose their edge in snow and ice. Better than BFG KOs in snow, hell yes, but I gave up on'm and went with FS winter force Dec thru March. If you are not offroading much you may want to look at Cooper's new ATW tire, they are biased for snow.
I'm moving towards KM2s or TSLs for summer and Winterforce or Hakkapeliittas in winter on all my trucks.