it will be close
if it's a 18 foot + a dove tail, it will work,
if it's 16 Foot + 2 food dove = 18 ft... it will be close.
although I could run my short bed on a 16 foot trailer, it didn't give good weight distribution.
Also, make sure the trailer is wide enough. more often than not a fullsize has width problems between the fenders, and getting out of the truck once it's up there...