wheel spacers are illegal, no one that i know of will install them or mess with the truck if they are installed. secondly, the 40's will rub really bad, not only on your leafs, but on the lower part of the bumper or valance, and possibly on the rear of the front fender. i have 37's with a 6'' on mine and if i hit a big bump and have the wheels turned the rub in the places i mentioned. i would recommend a bigger lift to accomodate the taller tires, and a more offset wheel to elliminate the rub on the leafs.