Vis mobility issues and truck camper:
I think that you should look at hard-side truck campers in the 22xx to 25xx LB dry weight range (add 600~750 LBS of cargo to those numbers), then, at a dealership with a stock of several models in your weight hauling range, pretend to go about your every-day routines (both get up onto bed; try bathroom almost all the way; pretend you are cooking; climb in and out of camper from the ground; etc...); one or the other should move around inside the camper as you pretend these activities to get a feel for life in a truck camper. Then, a few weeks later, do it all over again. 2500HD and 8.1L big-block (and you have the Allison transmission with this big-block) is plenty of truck to haul around the number I outline above. Also, you may want to consider Super-springs and air bags and beefier tires (~3900 LBS rated) and air bags just to level the camper, not as a primary suspension aid!
Also, consider that you MAY have to remove the camper from time-to-time. Get the dealership to guide you through a REAL dry load/unload run, too.
Good luck.
If the above does not work out for you, perhaps try a used Class B+ ?
Cheers,
Silver-
Silver
2004 Chevy Silverado 2500HD 4x4 6.0L Ext/LB Tow Package 4L80E Michelin AT2s| Outfitter Caribou