Darin, on the Escapees RV forum we have an active group of MDT and HDT conversion folks. Since the vast majority of our folks are HDT we're slanted more to the heavy truck side and we call our web site the Heavy Haulers RV Resource Guide, but in most cases the HDT and MDT rules are similar.
http://www.hhrvresource.com/ http://www.hhrvresource.com/
if you drill down in the sub menus there, you'll find a state by state listing of HDT registration requirements and comments from those who have gone through the process (successfully or unsuccessfully).
Unfortunately California is one of the states where it has been hit or miss, at least on the HDT side. Some have been able to get their heavy truck conversion registrations through as a "house car" or motorhome and others have run into a brick wall. I'm just guessing that there would be fewer issues with an MDT, but a lot of the same rules apply. I had already left Ca for South Dakota when I bought my HDT RV toter conversion, so no personal experience, just what other forum members have reported.
