Does Calmini still make an add-a-leaf kit? If they do, you take apart your rear spring packs and put in another leaf to make them stiffer... that's another way to get a little lift (though replacing shackles is MUCH easier - definitely start there).

Another option would be to get full custom leaf packs from Alcan - but that's more of an "i've modded the crap out of my truck and I need several inches of lift" solution