The Rolls-Royce Dart turboprop powered Grumman Gulfstream I proved to be quite successful as a large long range corporate transport, while the availability of an faster and more powerful turbojet
... powered model, the Rolls-Royce Spey meant that a jet powered successor was a logical development. Grumman launched such an aircraft, named the Gulfstream II or G-II, in May 1965.
[Text and Photo provided by Airliner.net: http://www.airliners.net/aircraft-data/stats.main?id=237 ]