So I just got through this process:
I pulled the seats out of the bus, and repainted it. Took before and after pictures with me.
I filled out the title MV-1 form, go the officer to come do the VIN inspection (which was not filed since we did a "model change").
The lady at the tag office had me fill out a "Model Change" form and she called the state office while I was there and she filed the paper work for me.
I have tags on the bus, the registration says HC (HomeCoach) which means it's legally an RV now and I'm good to go! God is good
I did have to pay taxes first, then get insurance, then I could get my tag, a little two step there.