I reckon the box will be fine, that thing weighs the square route of f-all compared to a camper.
It would see nowhere near the torque loading it would see in the VW, and it would accelerate that quickly anyway, if it did it would only be for a very short period.
A common misconception from people assuming light weight and knobbly tyres means little grip and low loads, but off roading at any sort of pace where a spinning tyre grabs an edge and suddenly has massive grip, or the wheel spins up when it lifts off and then grips when it comes back down, or just the general constant impacts and vibration, puts absolutely massive shock loading through driveshafts and gearboxes - it's one of the hardest applications for transmissions, clutches and drivetrains outside of top fuel drag race tbh.
If you go and buy a dog or sequential race gearbox you'll often see they're rated at different levels on the same 'box, and for something like 600lbft circuit use, 450lbft rally use, and 300lbft for safari/dakar....
I've got two of those boxes broken in pieces just from the old VW 2.1 aircooled engine that we used to run...and there's a reason my driveshafts are made out of vacuum-remelted spring steel