It is very possible. My brother works for a propane co. and in the 80's he converted many vehicles to the dual system. He had his car on dual fuel at one time. The best I remember there was a panel under the dash that had a choke cable like thing and a couple of switches on it. Yes you could switch from one to the other on the move. How it all hooked up I have no idea. The small tankes were made to go in the trunk and not occupy the entire area. It is very possible but I don't have any idea about the cost. Hope this helps.
