Complex sentence: The first model was a two-seater called "Arkley SS", designed by "John Britten" in 1970 (not to be confused with the famous New Zealandian motorcycle designer, John Britten).
Split into simpler sentences: The first model was a two-seater called "Arkley SS". It designed in 1970 by "John Britten" (not to be confused with the famous New Zealandian motorcycle designer, John Britten).