I have Carli's "soft" springs on my 2007 2500. I don't consider them soft with their Commuter shocks at all.
I'd go with Don's. Tough to beat a used Smarty tuner. They're in Marketplace all the time.
I was in Baja surfing and a guy with one invited me in to have a beer and get out of the elements. Sold. I got rid of my Toyota Hilux and bought a 1998.5 Ram 2500 and a Northstar TC800 popup. I never slept in a tent again.
The ULSD in Baja Norte is ours. I can't speak for Sur. I understand your concerns with government madated choked up diesels. The new gassers aren't exactly simple either.
I'm looking for a fiberglass camper shell,topper or whatever for a 2003-2009 Ram longbed. White in color. A front slider or drop down window is helpful.
Rack not necessary. Really good shape please. San Diego area but I can drive 50 miles for a good one.