I’d wager the older engines will do better at getting a heavy load moving from a stop in sand, while the newer tiny twin turbo engines will do better pulling through a mountain pass at highway speeds.
Towing that much weight “off road” isn’t going to be any fun, or a good idea IMO. Plenty of half tons can do it on the highway, but to get the tires I’d want for clearance in the dirt while not being unstable on the road or tearing up the drivetrain I’d be looking at a gas F-250 on something like 37” all/mud terrains.
If you get that rig stuck in anything other than sand, it’s going to be a nightmare to recover. Go watch the Matt’s Off Road on YouTube for some examples. It’s not something that’s going to come out with another stock 3/4 ton truck and your standard tow strap. I spent a lot of time in my youth getting lifted trucks buried and it was unbelievable what it took to extract them.
The physical size of a camper that heavy is going to be an issue as well. I’d rather pull a 6x12 utility trailer loaded with bags of concrete at the same 8000 lbs than something that’s 25’ long and 9’ high. You’ll find stuff happening like driving past a tree with half the trailer and plenty of clearance, then the tires hit an off camber spot and the whole top corner of the camper is dragging into the tree. Not to mention it’s not going to follow your tow vehicle with tight turns or paths through rock gardens, etc. Spend some time moving an open trailer around in a yard full of trees to see what I’m talking about. Also, that much weight moving around is going to be plain uncomfortable with the jerking, banging, and bouncing around.
Now, if what you actually mean is driving up a 5-10 mile forest or fire road and camping by a lake for several days, it might work fine for you. At that point though you should be fine with a standard camper or cargo trailer conversion, as long as it has sufficient clearance.