 Complete the following phrase:  Brabham cars competed at the Indianapolis 500 from the mid-1960s to the early 1970s. After an abortive project in 1962, MRD was commissioned in 1964 to build an IndyCar chassis powered by an American Offenhauser engine. The resultant BT12 chassis was raced by Jack Brabham as the Zink-Urschel Trackburner at the 1964 event and retired with a fuel tank problem. The car was entered again in 