Just remember this: advertised RV weights are not real-world numbers.
The advertised weight is with no water, no propane, nothing in the rig, no options, probably not even any grease on the wheel bearings or balancing weights on the wheels. I'm pretty sure they even fill the interior with helium.
I don't understand the insistence on the least-capable truck to do heavy towing with, in my experience with many trucks campers and trailers that's a mistake, but if that's what you're dead-set on then be conservative on the trailer weight. Add 1000 - 1500 pounds to the claimed trailer weight.