What year are you talking about? How big is your truck...3/4 ton, 1 ton...??? I have never seen a 1/2 ton flatbed on an original Dodge, but there could have been. If you want to do that conversion on a 1/2 ton or car chassis, here is an example of a Model A Ford 1/2 ton pickup/flatbed conversion that I used to own. A lot of bed or box manufacturers were independent and were dealership add ons.