Thought you were dealing with some weight issues. I'd still think about torching the kingpins off an old lightweight straight axle, if laden weight is a deal.
Not the case - sounds like what you need is a Chinese made commercial garden wagon which can be picked up in my area for around a hundred bucks at Tractor Supply. Modify as required.
(edit) Forgot that you want to use your stuff - then go look at the garden wagon. I was thrown off when you stated the box frame would be super duty, assumed that you wanted the weight carrying ability to be up to the frame standard. (edit)
Bokrijder screwed with this post 02-17-2013 at 07:49 AM