Dude I've read the whole thread, and happen to tow a lot from a 1,000lb off road trailer to grossing 45K with my superdutys. If you want some unsolicited advice, Any tow rating the factory puts on a vehicle has a large safety margin. You freely have repeated your set-up weight 3,400 lbs and that is "too close". I would submit that it is not. Especially, if you have the four door. (It literally makes no sense to have the 2 door and 4 door rated and both engines rated the same) I actually think the numbers are just a place holder and NOT the final numbers and the Ford people fielding the questions are just repeating what the current info states.Camper weighs 3395lbs loaded (gear, 40gal of water, diesel, food etc.).
Just to be clear the 3,500 is a tow weight rating not a GVWR. Place more load in the Bronco if it makes you feel better. That said, even if the final rating is 3,500 I would have zero problems hooking up to 3,400 in a properly loaded trailer. I'd get the 2.7 and the 4 door, I personally would not want to pull 3,500 in the short wheelbase 2 dr.