To carringb,
I've never heard of being able to rent a truck with a fifthwheel hitch but it sounds like a good idea.
I will only be towing 2,000 miles a year and then driving it another 13,000 miles a year.
I ended up ordering a 2016 F350 crew cab shortbed with the 6.2/4.30gear combo a week and a half ago. The excessive wait is another reason why I am second guessing. I have a brand new fifthwheel sitting in my driveway and the dealer is telling me it could be 16 weeks.
I did borrow my friends 2012 f350 6.2/4.30 gear combo to tow the new trailer home a few days ago. It did fine and only dropped down to fourth gear once going up a bridge on the highway.