If you want a lot of travel with a ttb you'll need longer coils, shocks, radius arms, drop brackets for the axle beams and most importantly, a good steering setup.
The 6" Skyjacker kit that everyone has been talking about has all of that, though it'll probably come with a Pitman arm that isn't quite long enough. (FA400 vs FA600).
You can also piece together your own kit like many of us have done, which is what I would recommend. Skyjacker 6" coils, Skyjacker drop brackets, make your own radius arms, F-250 shock towers and build a swing style or custom K-link steering setup and you'll be able to get anywhere from 12-18" of travel, limited by shock choice and placement.