measure how high your roof sits now and add 3.5 + 2 and then your tire size. The leveling kit only raises the front correct. You want to run 285/50R20 what do you have now? I think parking garages are 9' and you wont be that high. Im not a fan of the big rims i like the fat tire look id keep the 17s or get 16s but its your truck. post some pics.