The 1140 will be too heavy for a SRW unless you make upgrades to the wheels and suspension.
If you do not plan to tow anything more than 3000 lbs, the 3.55 gears will be fine. Towing heavier will result in you driving mostly in 5th gear and downshifting to lower gears on grades unless you are on flats with no headwind. If you drive faster 65 mph with your truck camper, the 3.55 gears may get you better mileage. Driving empty will get you better mileage with 3.55's.
4.10's will give you a lower first gear in addition to top gear which helps on steep terrain or difficult campsites. You will be able to drive in 6th gear more often and use the full range of the transmission but may find it winds too much if you have heavy foot on the go pedal.
I rarely drive my truck faster 65 mph unless it is rolling down a gentle grade and have my gearing selected for my driving style and combined weight. Figure out your usage and gear appropriately.