In this post in the Van Life Q&A, a user asks:
Does converting a van require a change in registration / insurance?
You don’t have to, but often there can be benefits. Some states have lower registration fees (while others are higher) and the insurance can be lower since there are statistically less incidents involving RVs. Then again, if they deem the value to be significantly more than the van it could increase your premium.
Call your agent and talk to them and research the DMV fees, and any property tax rates if applicable.