The Griffin may have been the last aircraft V-12 produced. According to Wikipedia, it went out of production in 1955.
It looks like the Allison V-1710 was out of production by 1951.
The Pratt & Whitney Aircraft R-2800 went out of production in 1960.
The Wright R-3350 Duplex Cyclone was produced through 1957.
The Alvis Leonides was produced until 1966.