Word of caution about conversions, I suspect that is what JRBar's issues were (are). Although the trucks, whether MDTs or HDTs are built to the trucking industry standards of quality (read - reliable and bullet proof), the conversion portions are built to RV industry quality standards (read - crappy). The emphasis is on paint. chrome, leather, wood and glitz, but don't look underneath. I have lots of experience.
Pretty, isn't it?
Took me months to fix "their" wiring (not the truck manufacturer's wiring).
Finally junked it all and built my own dashboard.
How about this one, pretty too?
This way their idea of modifying the original truck harness to wire the 7 pin RV plug.
This was my idea of doing it (right).
Unless you are handy at doing it, or purchase an extended and comprehensive warranty you are going to be skinned alive, as JEBar says. You bring garbage like this to a Freightliner or International dealer, they are going to look at this and say "Oh boy", it's not their stuff so they will have to figure out what the upfitter did "to their truck" first. Lot of hours at $60-100 bucks per hour.