I have a Black 2005 Tahoe, LS Model 4WD, that came with 16" wheels. After much research and thinking, I went with 20" wheels and 305/50R Toyo AT Open Country tread. The wheels are by Ultra Motorsport - 6-5.5 Ultra Type 261/262 Black Medium Offset. Gave a bit of lift, and Les Schwab adjusted torsion bars to lift the front just a bit to level out the ride and provide tire clearance in front fender wells. Had to trim the driver's side fender well plastic about an inch up (front side) as tire would rub on hard right turns.
Have gotten nothing but compliments on the wheel tire selection since.