Welcome to the CRVL forums! To help you learn the ins and outs of these forums, this "Tips, Tricks and Rules" post lists some helpful information to get you started.
Most of our rules boil down to two simple over-riding principles: 1) What you post should provide good information (like your introductory post), and 2) Any response to someone else's post should make them feel glad they are part of this forum community.
EVERY SINGLE state has its own laws regulating insurance. Which means that an insurance company that will insure a DIY conversion in one state won't necessarily insure the same vehicle in another state.
www.escapees.com is a good resource for info. An independent insurance broker in your state is another good resource.
When I bought my van, I told the agent I was buying it for camping. He was good with that, and my van is insured as an ordinary passenger vehicle, with the contents covered by my renter's insurance. (One of many reasons to do a no-build build - I could clear everything out in an hour, leaving behind an ordinary cargo van.)