C-133 Engines

A Boeing B-17 used as the testbed for the Pratt & Whitney T-34 tuboprop engine. In 1945 the U.S. Navy funded the development of a turboprop engine. The T-34 was produced from 1951 to 1960, but never used in a U.S. Navy aircraft. The best known "user" was the Douglas C-133 Cargomaster. Date: 1950 Source: U.S. Navy Naval Aviation News October 1950

Thanks to Andy Fleming for pointing out this interesting post in Wikipedia.

Then Cal Taylor replied that he "used that photo as the header shot in Chapter 6, Engines and Propellers" of his book Remembering an Unsung Giant . And he adds, "That airplane was later restored to a WWII B-17G configuration by an outfit in Florida. Sorry, can't recall their name."