I'm getting ready to purchase an 07' 2500 duramax and I want to put a 6" lift on the truck. My concern is whether or not an 18" rim with 325s or 33s will fit in the spare tire compartment. I travel a lot so I don't want a bicycle size spare. For those that are wondering, driving any length of distance on a small spare with three other large tires can do damage to the rear differential. I've been down this road already with my current f350. I had a flat with 325's and the spare was way too small!