AZ I don't know but in both MA and FL I had an RV registration for my F550 / Bigfoot combo. Kind of played dumb and repeated that it was a custom built RV (Did have a utility bed cut to fit the camper), and the camper was basically never removed, and it had plumbing, toilet, tanks, etc.
Saved a lot of $ in MA over registering a 'commercial use only' F550