I had 10' service body and not only floor was 7" above the frame, but I had to add 4x4 planks to clear sides with camper.
Having basement camper that made for 13-6 total height. Not too comfortable and costing extra fuel to push that frontal area.
Flatbeds add 4-5" to the height.
Lot of variables, so carry tape measure with you checking it out.
On the other hand, the original Cab & Chassis on 2006 F350 had stronger suspension than regural bed trucks.
I had no problem carrying the heavy body and 6000 lb camper set 2 ft behind the cabin.