The FJ-4B was in front-line service until 1962 (year of its last carrier deployment, aboard USS Hancock CVA-19), and with the reserves for a few more years.
A radar-equipped night fighter version of the two-seat F9F-8T (TF-9J after Nov 1962) was proposed by Grumman in 1955. It was to have carried an AN/APQ-50 radar and was to have been equipped with an all-missile armament. However, the performance was considered insufficient to warrant production.
In 1961, Grumman proposed a modernized version of the F9F-8T with updated systems and a Pratt & Whitney J52 turbojet in place of the J48. However, the Navy selected the Douglas TA-4F instead, and the updated two-seat Cougar project was abandoned.
Now, what would replacing the Pratt & Whitney J48-P-8A turbojet (rated at 7,250 lb.s.t. dry and 8,500 lb.s.t. with water injection for take-off only) with a Pratt & Whitney J52-P-8A turbojet (rated at 9,300 lb.s.t) or even a J52-P-6A (8,500 lb.s.t. dry) do for performance (climb rate, top speed, etc)?
I have a good idea what the lower fuel consumption (.86 lb fuel/lb thrust/hr vs 1.16 lbf/lbt/hr for the J48) would do for its range... and fitting it with the APQ-50, allowing it to find a place aboard CVSs for CAP - that might perhaps allow it to continue in deployed service long after its historic 1959 withdrawal to reserve squadrons (where the historic F-9Js & AF-9Js [F9F-8Bs] served just as long as the AF-1Es [FJ-4Bs]).
