Yeah, tell me about it...I see lots for sale with the box but those add $20-$30K to the price and reselling them I suspect will be difficult and I won't be able to get anywhere near that money back out of it. The 450 DRW 158 does seem to be pretty common...I want that version as my needs are very different from yours. I want the capacity to load ~800lbs of motorcycles on a custom rear rack. I'm a park and play guy...need my rig to delivery me and my bikes to cool riding areas then I park it for a few days and go Moto. Plus, I want a bigger box as I plan to spend a lot of time with it and the size will be much appreciated from my current RB E-350 van.I had no luck with any dealers, none of them had any or could order one anytime soon. It was also very difficult to search for them and specific one without a box, not to mention most of them were larger and duallys. I think you may have better luck trying to find the 158 Dually you're looking for.
I ended up lucking out because @UjointoffroadCO let me know of one that was sitting on a dealership in Florida and grabbed it right away!
I did find a couple more "commercial dealers" around the Atlanta area and I plan to visit them soon.
How did you get your Chassis home from FL? As I understand it they are not drivable off the lot. But I suspect a wood back with flatbed and 4x4 bumper would make it look road-worthy enough, right?