There have been several people that have done it and I myself have looked into doing it with a Volvo 730. There are several threads about it over on the skp forums.
In short, you need to get a LEO to sign a vehicle modification form for you certifying that you meet the IN requirements for a MH. I do have that info somewhere but since my project has been temporarily postponed, I am not sure where it is.
Anyway, once you get that form signed, all you need to do is bring it into the BMV and they will register it as a MH.
Like I said much more info over at skp...look for posts by "pete&carla" to start.
Of the people that have done it they have all said that it takes 20-30 min as long as you have the body mod form signed already.
You actually thought the BMV personnel would know what you were looking for?!?!?!
