This experimental artillery piece is a M2A2 Terra-Star 105MM cannon developed by Lockheed and Rock Island between 1969-1977. Self propelled with a small gas engine (Box on the back) with a standard 105MM gun mounted on it.

Looks more like something used in the Movie Damnation Alley (I used to see the actual vehicle parked next to a gas station near Burbank for years).