Short boxes are better with trailers than a long box. For starters, the truck is 2' shorter (if the same cab), and it makes backing way easier (can jackknife easier to when backing into a tight spot).

 

I suggest going and towing a bumper pull toy hauler around 25ft and get a feel for that. Trust me, 10k pounds is HEAVY and you'll probably be getting at best 7-8 mpg most likely less. I've towed our 25ft toy hualer fully loaded, i dont know the exact weight but it definitely made the HEMI run thats for sure. The truck handled fine even though i have a 1500 just power wise was just not up to the task. We now pull it with a ford f350 7.3 long bed diesel and you forget it is even back there.