Thanks all.
Since I will need to reinstall the driveshaft at my destination and won't have the place or tools I might look into a trailer rather than a dolly. The rig I'd have would be my 2011 2wd Explorer with towing package and 5,000lb hitch. Problem is that when I enter that info and the Bronco as the trailered vehicle their calculator won't allow me to go further in the rental. If the rating was listed as 5,500 it would be permitted. So it seems there is a 500lb discrepancy I'd need to work around. I can portably list the trailered vehicle as something else (Escort or such) and rent. My concern (other than liability in the event of an accident) is am I pushing my Explorer (with 189,000) too hard?
U-haul requires that the towing vehicle weighs 750lbs more than the combination of dolly and towed vehicle. Tow dolly weighs 750, Bronco II is listed at 3,500lbs, Explorer is listed at 4,500lbs. So, by U-haul's calculations, you're 500lbs too heavy. So, its only partially the hitch, and more the weight of tow vehicle that is issue.
You also need to read the fine print on the towing guide: 2011 FWD Explorer is limited to 2k lbs unless a weigh distributing hitch (WHD) is used - and u-haul trailers aren't set up for WHDs. (Personally, I wouldn't want to tow something as heavy as vehicle on tow dolly with FWD without WHD - not enough weight on driving tires). My F-150 has same issue - lots of capacity with WHD, not so much weight carrying so u-haul really limits it compared to ultimate from Ford.