i and many others have run 33's on that set up. its a dog, top speed on the hiway is 65 downhill, and you won't see fifth gear anymore. the ax5 trans doesn't hold up well, and the axles aren't rated for a 33" tire either.
how big should you go? 32" and 4.88 gears. that would be set up to put you back where it was stock, but i wouldn't spend my money that way.
how big can you go, 33" is not uncommon, and i've seen guys run 35's on that set up as well. they break stuff usually. somehow i never had a problem running 33's, some do, some don't.
the catch 22 is, regearing is the best thing when running larger tires, but do you really want to spend money on the stock axles?`