To be truthful I'm not sure about being street legal, I have not tried nor have I ever seen one street legal in Utah. There is a lot of lenience of ATV's and SxS's in certain areas, especially around the Piute Trail areas as the trail goes thru some of the towns.
This is the main reason I'm building a baja(also have a Manx), so I can be street legal.
Wyoming on the other hand is quite different. They have a permit that you can get that makes it legal to ride on any road except the interstate. Only basic safety items are required. Not unusual to see a SxS or ATV on the streets in Wyo. Your buggy would def. be allowed on the streets of Wyo. with the permit.
Arizona-How about some detail shots of your buggy, looks pretty cool. Is that a door I see to get in? Motor, trans?