I am running a 295/45/20 and am looking at new tires. Something a little taller to soften the ride. The 295s never rub and are only 30.5" I think I am going to go 305/50 which is 31.9. I think it wont scrub. Keep in mind my helper airbags in the back. They add 3" to the rear at about 35lbs of pressure.
The link below has some pics with the rear bags empty. they are slam air bags from summit and you have to have the ones for lowered trucks or they won't fit. I also have limiting straps to keep the bags from being damaged if the rear is lifting by the frame instead of the axle.
Putfile Photo Album Detail - Truck
you can via the link see my whole truck album of pics from way back when i first bought it.