c7,
There are a few, very few 17 inch tires that are up to the rigors of the truck camper mode. I made a survey of 16 inch, 17 inch, and 18 inch tires to see what the maximum loading would be. The sad fact, it least in my survey, is that 17 inch tires, as a group had the lowest load rating. Then came 16" and finally 18" tires had, as a group the highest load rating with some getting up to the 4000 pound range, plenty enough for your TC lashup. So, I could not find one recommendation for you.
The highest load rating of AT3's or GeoLanders, LT285/70R17 size was 3195. That's not going to get it. My 315/75R16 AT3's are 3860 pounds load rated. That's 7720 pounds, per axle loading.
If you have the wherewithal, check out some 18 inch wheels, preferably steel, with a high load rating and use any of the many sizes that get you to the high 3XXX range or higher.
I wish it weren't so.
jefe