I would suspect it depends on what kind of "Camping" you'll plan on doing.
On the highways mostly, paved, I'd probably go with the highest for gas mileage.
If Boonie camping, dirt roads I'd probably go for the 4.10 (it's what I have now) for the lower gearing for dirt roads etc. I get apx 9.5 mpg, I don't know just how much difference the 3.55 would make, but guessing some on the highways.
Not much help, but something to think about...
If I were to choose again, I'd probably stick with the 4.10 and suck up the mileage loss if any..
I "Try??" to cruise around 63-65 mph.. heheh, doesn't happen all the time.. but that's the goal..
Hope that helps, congrats on the new 1140, fun...