"Originally built as the five-seat Aztec A in 1959, the Piper PA-23 evolved into the six-seat, longer-nosed Aztec B in 1962. The Aztec C, introduced in 1970, had redesigned engine nacelles and a longer nose and Aztec D was externally similar. The latest version is the Aztec F. Aztecs of various marks are fitted with turbo-superchargers. As is the case with many American light aircraft, new designations often denote updated equipment and fittings rather than any changes in outline. The Aztec F cruises at 338km/h for 1335km."
-Jane's