[Mike C]

1 1/2" is max for lowering shackle. Anything more would stick out the bed! But removing the overload leaf and the shackles gives you almost 2 1/2". But you will not regret buying springs and doing it right the first time, but you might regret NOT doing that. But in the case of the shackles, they can be sued with the 4" springs and you could add the overload back, so no rear loss except a new spring center pin.