As Kyle said, I have been playing around with the rear set up on my truck for a while now. Currently the setup is at 75mm longer custom top leaf and modified spring pack, Monster Rides extended shackles with an extended brake line and extra long travel Monster Ride shocks. It has been working flawlessly for over six months now, and I get fairly decent travel from it.
Next satge of R&D will be to modify the handbrake cable giving it more length as Im fairly sure that is holding up possibly 2 inchs of unused travel in the shocks, custom shaped shackles and possibly an A-frame shock mount setup.
Continuing the quest for more flex....
Cheers