On my 4x4 I'm running stock P255/65R16 all weather which they recommend 26 psi cold back and front. On the bad dirt roads and in the sand I run them at 20 psi cold which seems to work good and lessens the bounce/shaking. The xterra has only been running on dirt roads for the last 16k miles which are spread out over 4 years (about 4k per year).

I would like a softer or less vibration ride on the dirt washboard but a firmer ride on the highway to counteract the understeer.

I'm looking at the HD 5100 Bilsteins for the front and the rear but does it matter if I get the ones for a non lifted X or the ones for the an X with a 3" lift? How much firmer than OEM are the Bilsteins and is the firmness of the non lift model and the lifted model the same? I don't mind a firmer ride on the highway as long as the ride is also better on the washboard and not stiffer.

I'm asking all these questions because when I'm not in Mexico my other home is in the Caribbean so in either place I just can't mosey on down to an auto parts store and check out the goods. I'll have to order online and hope for the best so I want to make the right purchase on my first try. I appreciate any help that you might be able to give me.