iJeep......
I re-read your post.
Yes you will have to have a hauler bed. You CAN NOT pull a 5th wheel with the F350 type dually beds on an F650...It is just way too tall.
The tallest truck that I was able to tow my 5th wheel with was my old 2004 F350 single rear wheel. It had 35" E rated tires, air bags, full Bank Big Hoss kit, and Donahoe Racing 4.5" Lift Kit.
Here's a picture of my old truck.
It towed pretty good, but It doesnt even compare to an F650 with Cat C7.
Thanks,
SoutherHick