I've got 275/70R17s on a lowered truck. 3" shackles, removed overload and 2nd leaf, and t-bar bolts basically all the way out. General Grabber ATX. I'm running a Hummer H2 wheel. I think the backspacing / offset plays a big difference in how easily they fit. I have extremely minor trimming of the lower valance, and they clear perfectly. No rubbing at all.
I only run these wheels in the winter. Best part is that they're the same size (diameter) as the 305/50R20 (on 20x9s) that I run the rest of the year, which means that I don't have to recalibrate the speedometer. The 305s do rub the rear of the fender liner a little bit in reverse at full lock.