If 2 1/4 is all you have, I think you're better off getting a 2" kit because the kits usually give you more lift than what they say they do. Especially if you get an Autospring leveling kit.
I wouldn't go 2.5" unless you want it nose high. You usually get more than what they say, not less. I got 2.5" out of a 2" Autospring.