Honestly, I would do a 4/6 Drop if I were you, you should be good. I dropped my friends truck, hes running a 265/40/22 tire its just about 31inches tall I did a 3/3 drop on it and its not low enough there is enough room up front on his truck to drop it another inch and not run into problems. The rear could also come down 3 more without a problem. Here are some pictures of his truck after we got done with it...
