Subsequent revisions to the MP design were soon made, resulting in the model MP3 which has the larger "ZD" engine of 305 cc which produced . In May 1960 the longer MP4 arrived, featuring roll-up door windows. In August 1961 the doors were modified, now incorporating a triangular vent window and a chromed side strip. In September 1962 the final iteration, the MP5, arrived. It was again somewhat larger than the earlier MP4, with maximum length up to and cargo space increased by , to a total of . As a matter of fact, nearly all body panels were altered in some way, with new marker lights installed, redesigned doors, a blunter and more rounded front, bigger vent openings in front of the doors' leading edge, and finally a solid metal roof rather than the earlier fabric-covered opening. The MP5 also gained more chrome trim, around the headlamps and elsewhere. April 1963 saw the introduction of automatic oil mixing for the two-stroke engine. In August 1969 new safety regulations required certain lighting changes, a driver's side headrest, and seatbelts. The MP5 remained in production until December 1971, and on sale into 1972.