There are some low sided service bodies out there. A friend of mine that owns his own car lots bought an F-350 with the regular service body that had been wrecked. He had one of the guys in his shop repair the body work to the cab and remove the damaged body. He then took it to a shop that specialized in service bodies and had a low sided body installed along with a gooseneck hitch. He used this truck for several years to tow one of those 4 car trailers to move cars between his car lots. This truck set up this way would also work to tow a fiver. The bed sides, from what I remember, were actually lower than a standard pick-up bed.