[hewittca]

This is an interesting question since, as you mention, most do not want a softer spring in the rear. I don't know the specs on all the different springs available (and there are quite a few!) but I have experience with several.

I've had heated stock springs that dropped the truck about 4". To be honest, these weren't that bad when cruising and I could load them down to max payload with no problem. Ultimately I decided this wasn't the "right" way to do things.

Then I went to a 5" ECE. This spring was very soft compared to my heated stock spring. It was also quite low, requiring a C-notch. I would bottom out routinely with this spring. One time I put a couple hundred pounds of dirt in the bed and the truck was completely bottomed out on the ride home. The only travel I had was in the tire sidewalls. That made for a very bumpy ride! I've heard that this is just a Chevelle spring that also fits the C10, but I've never confirmed that. This may be why it's so soft in a truck.

Lastly, I moved on to a 4" HD spring from CPP. This spring is definitely the best I've tried so far. It has a nice ride quality. A touch on the firm side, but it pairs well with the 3" CPP drop springs I have on front. I'm getting about +/- 3" of suspension travel with this spring. It also performs admirably with some weight in the bed. I've had it loaded close to 700 lbs and it still rode really well. I didn't even bottom out at all.

I had considered the airbag trick that you talked about, but after going with these 4" springs I don't think I need to do that. The ride height is where I wanted it and I can still haul some stuff around. Hope that helps!