Wisconsin DMV has an article:
https://wisconsindot.gov/Pages/dmv/v...onversion.aspx
Basically, if you want to register as anything but a bus, you must repaint, get rid of the flashers, stop sign, signage and front bar. Once you do that, you can register as auto, (regular) bus, heavy truck, light truck, or special X. If you want to register as an RV (motorhome title), there are more requirements like 4 of the following:
A potable (drinkable) water supply including faucet and sink that is self-contained or connects to an external water supply
Ice box or refrigerator
Self-contained toilet
Cooking facilities
100-125 volt electric power source and/or LP gas
Heating and/or air conditioning