It was bailed to General Electric in January 1966 to test the General Electric TF39-GE-1C turbofan engine, developed for the Lockheed C-5A Galaxy military transport.
Also used to test General Electric's commercial variant CF6 family of high-bypass turbofan jet engines used in Airbus 300, 330, Boeing 747/767, DC-10-10, MD-11, and Air Force One.
CF-6 high-thrust variants produced around 69,800 lbf while the B-52's J-57s topped out at 13,750 lbf of thrust per engine with water injection.
My Air Force Col. Father retired as head of J-57 management at Lackland AFB.