Nbs Lift Question

[Jameson]

I have a NBS 2007 CC Silverado Z71 with the 4.8L and 3.42 gears so I know I cant run big tires. Im wondeirng if running 285/55-20's will be a problem? Also how much lift will I need to clear these tires? I saw a truck on ebay with 3" Suspension (i still cant find that kit) and these tires and it looked great. Are these tires too big for my engine/gear set up? Its only about 1.5" taller than stock. Thanks guys.

[Controller]

I have 275-55-20 on mine with 2" leveling kit and the tires rub my mud flaps.

Hope this helps.