The 6' 4" short bed Dodge/Ram Mega Cab will work fine for towing large trailers. Its the same 6' 4" bed as in the CC short bed trucks. Short bed trucks can have a bit more payload than the heavier long bed truck.
Any length of of bed with todays trucks with 140" wheel base and longer has no problems towing a trailer.
IMO too much is said about a long bed some how being superior for trailer towing duties as far as handling goes as today we have some short bed trucks with a longer wheel base than some long beds.
IMO it may come from years ago when long bed vs short bed made a difference as many short bed trucks had a 118"-120" wheelbase vs the long bed with a 130"+ wheelbase. So sure the long bed truck with the 130+ wheelbase was the better choice for towing larger trailers.
