Brakedwell:
......The success of the KC-97E led to Boeing’s development of two more models. In April 1952 the corporation announced the KC-97F. Featuring improved engines and instrumentation, 159 F-Models came off Boeing’s Renton, Washington assembly line. But the biggest contract came in mid-1953, when the Air Force purchased the KC-97G.
The –G offered much improved flexibility: 700-gallon capacity drop tank was added beneath each wing; the upper deck tanks of the –E and –F, used for air refueling, were moved into the lower fuselage, so the –G was immediately usable as a cargo aircraft.
The –G model soon became the major production version of the KC-97. A total of 592 Gs were built before the KC-135 replaced it on the Renton assembly line in 1956.