Bayer
I have called and talked to these folks, as I am also interested in a Cummins-powered crew cab. They said the conversion typically costs in the 11,800 - 12,000 dollar range. When they understood that I was a private party and not a dealer, they sounded surprised. Evidently, they don't do many for private individuals. I believe that Auge Bros. Dodge in Belen, NM has sold a couple of Crew Cab conversions, although I don't know which company did it. They looked top quality, just like the bayer units.