Leading to:The GM B-body was introduced in 1926, and had at least 12 major re-engineering and restyling efforts, in 1937, 1939, 1941, 1949, 1954, 1957, 1959, 1961, 1965, 1971, 1977, and 1991; along with interim styling changes in, 1942, 1969 and 1980 that included new sheetmetal and revised rooflines.
How about them apples?The Rear Drive B-body was the last platform design to have the gasoline tank filler port behind the license plate. Exceptions included all station wagons, as well as all 1961-64 cars - which had the tank filler in the rear fender on the driver's side and 1965 Buicks which had their fuel filler door above the license plate. Also the Pontiac B-Bodys from 1941 till 1948, they had the fuel filler door in the rear fender on the driver's side. Very likely this would also have been the case with the B-Body Oldsmobile and Buick.
At approximately 12,960,000 across four marques not counting 1966 full-size Chevrolet station wagons (production of 1966 full-size Chevrolet station wagons is unknown but a good guess is about 150,000) the 1965-70 GM B platform is the fourth best selling automobile platform in history after the Volkswagen Beetle, Ford Model T and the Lada Riva.[3]
https://en.m.wikipedia.org/wiki/GM_B_platform