If you buy 3" kings, they come with an adjustment session usually.
Personally, I have the carli 2.5" lift f250 front springs (linear rate) and they were much better than what was on the truck originally and not too soft (though my rig is lighter). I shaved 1" off the springs, and they sank a bit due to the extra weight of my rig, which put me back at my original 1" lift.
My recommendation would be to do the carli in front, and then have deaver make you a rear spring pack or use your local spring fabricator. They just made mine, so they'd be able to extrapolate for your weight pretty easily from mine. The deaver provided a huge increase in ride quality. Huge.
I woulndt put anything smaller than 3" kings and I'd consider 3.5". I'm changing my rears out to 3.5".