I have got a Dodge 3500 dodge diesel that isnt the commercial deal w/ the extended frame. I have a 8ft wide bed that is 9ft long on the truck now. How far over the axle can I extend the bed? I want to add 1 or 2 feet of straight platform and then a 2-3 ft dovetail. What do yall think? One of my worker's dad can do all the metal work CHEAP. Also how big of a isuzu-style box could I fit on there? 14ft? Any help is appreciated.