2.5" should be the most that you want to go, even with that height, the front end is going to get beat up pretty good. If you're 4wd, don't go over 2". Most guys go with either the 1.5" or 2" leveling kits.
With 2.5" +, you'll also need to lift the rear up a bit.
With 2.5" +, you'll also need to lift the rear up a bit.