Just bought a set of the FZ7 (Magnum) wheels from the dealer - Dodge or Bellevue (Wa) for $2,500. They came with 265/45R20 Pirelli Scorpion Zero's. At that size they're 0.76 inches bigger outside diameter than stock. I was a little worried about that, but they seems to fit. And they really fill up the wheel well, which looks nice. And the dealer made the appropriate adjustment in the computer so the speedo would be right.
It's amazing how much better the car looks. I was worried that I wouldn't get the "bling" without going to a 22, but man, these look good. There was literally a crowd in the service bay looking at the car when they brought it back in.
The ride is definitely better (no bumpier, and much less "floaty"). Cornering is much better. Not sure about accelleration yet. With the bigger and better quality tire you can't break them loose, and that was really my only metric for stop to go accelleration.
My only concerns are that there is a bolt sticking down above the inside of the front tire that now only clears by about 1/4", and that it doesn't look like the tires are going to make it inside the rear wheel well if they compress that far. I guess we'll see.
Sorry for the poor quality pics and dirty car.