Tucking that much tire is going to wreak havoc depending how low you go. I'm running 18's/19's, 5" ground clearance to the rocker and a stock tube wouldn't even come close to fitting my 345/30's in the rear. Don't even think about the front. Definitely can not go too low without losing the front inner fenders and raising the wheel tubs in the rear. Best thing to do, set it on the ground at the ride height you want, test fit the wheels and see what you need to do to make it work. You should plan for at least 3" of compression, plus an extra 1/2" or so clearance. Coil-overs or air can make setting ride height easier, and using an RMS kit or HemiDenny's front end kit can make it easier on the inner fenders by eliminating the need to mount the shocks there. Proportion will be key for 20's in the rear and I would say, like others, no smaller than 19 up front. Can be done and done well, but will take some planning. I have to say though, I'm surprised at how well I like that wheel in there. I have to keep looking at that wheel, looks REAL tough. I like it!
Here is where I'm at with my setup.
