Thing about the KYBs is gas shocks tend to be a bit harsher. Not as easily collapsed on impact with a bump so a bit more jarring than say a hydraulic shock would be. I've read that gas shocks add up to 40 pounds in spring rate to your existing leaf spring rate. Just a couple of things to consider. Hard to find a good hyd Shock these days. All modern cars use gas shocks I believe.
I've got a practically new set for sale if anyone is looking..