Im running 20X8.5 up front with 245/45/20 tires and 20X10 on rear with 295/40/20. The ride is pretty good. I put all new KYG nitrogen shocks all the way around. The rear end has bottomed out if I put 400-500 pounds in the bed. Just make sure to keep your rubber stops in place! On regular stance the frame is about 3" from the frame.
Here is a pic to show the space between frame and rear end. Notice the bumper stop was still out
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