First, if you add a space and width=600 in the img tag, it /will help the screen format right for the rest of us. :)
I suppose you have to make your own hitch for a chassis frame. I don’t think it would be that big of an issue for a great welder if you overbuild it.
As far as the boxes go, how much weight do you plan to put in them? Ujnless you plan to put a lot in them, there isn’t any reason to put them low. And if that is the case, you’ll likely have to reinforce the boxes. I’d look at som commercial solutions like the Douglas bodies to see if you can copy them or buy from them.
http://www.douglasstruckbodies.com/mobile/#page-gallery
