There are several truck service companies out here (south dakota), and else where that sell converted U-Haul and Ryder trucks. the conversion is not difficult at all. Cutting down a long frame is much easier than extending a frame. Good used dump bodies are available all over, you will also need a PTO wet kit for the hydraulics, also not a big deal. I am looking at doing this as business builds. Also check out http://www.lapinetrucks.com---
they have many available. Let me know if you need more help.