I know you guys like pictures and since I posted this late in the build I thought I'd catch you up on a few things I posted on another forum.
This is how I did the dualies:
I used M8x90mm bolts, cut the shank down to 35mm, then drilled and tapped M4 thread into each end. This allows the M8 bolt to secure the first wheel, and provides the hex for the second wheel, which is then secured by a M4 bolt. Locktite will be a must!
This is the begining of a dump trailer to go on the back that I did when before I had the parts to start the tractor unit.