I have heard that the government announces amnesty every so often, for cars that may have been brought into the country without payment of duties. The deal is to pay the duties and some fine and your car would be legalized in every way. Not sure if there is a timetable when this amnesty is announced but in my opinion this would be the only way to register your car. Until then you can take a chance if you wish and drive it around town with plates off your other car.