add a coil

www.outerlimits4x4.com theres a few there that have, isnt a cheap or easy job. being in the 1000's for a proper job.

Outback suspension in Croydon Vic (03 9725 8672) do it. Also Fred's 4WD Conversions in Harlaxton QLD (0407 063 126) fit them and sell DIY kits for some vehicles. It's a pretty good idea and will improve your ride quality or increase your carrying capacity - not both. Should cost a bit over a grand including greaseable shackles. Air bags however being adjustable can improve ride quality and increase carying capacity. They're a bit dearer though. There are plenty of threads in the archives about airbag springs.