Try to get it insured on a commercial, but for personal use policy, instead of an RV.
Having it titled as a motorhome without it actually meeting the requirements to be one, will probably work against you. I'm not sure how you accomplished that based on your intentions to make it one.
On a commercial policy make sure you read the fine print. Often there's a mileage radius limit placed on the vehicle. It can be as little as 25 miles from the policy holders address.
Insurance companies have a problem determining a replacement value on DIY conversions. Having the conversion done professionally results in a paid receipt for the effort.