There is a guy who lives close to me (I don't know him) who put a service Body on his 2500 that he uses to carry a large Lance camper.
It might have been a custom or semi-custom job though because he started out with just a flatbed, then put the boxes on. I t seemed like he had some trouble because the flat bed was on and off the truck several times. Now that its done, it looks like it works pretty well, although I question that much weight on a 2500 considering the camper alone is probably close to 4000 lbs.
If I see him outside sometime, I'll stop and chat with him, because I've thought of doing this myself.