The long bed is 89 inches in length and 48.5 inches in width. I am not sure about the length of the short bed, but 77 inches is stuck in my head. It sounds like you will be doing a lot of work for 12 inches. I would consider starting with a shortbed truck if you want a shortbed. I would also consider staying with the longbed for the type of power you will have. The longer wheelbase will help to keep you straight.