The total length of the J-2 rocket engine is 133 inches, but what is its nozzle length from throat to exit?
FWIW, here are J2-S numbers.
The paper "Altitude Developmental Testing of the J2-S" gives the throat diameter as 12.192 inches and the expansion ratio as 39.62.
Thrust Chamber — The tubular-walled, bell-shaped thrust chamber consists of an 18.6-in.-diam combustion chamber with a throat diameter of 12.192 in., a characteristic length (L*) of 35.4, and a divergent nozzle with an expansion ratio of 39.62. Thrust chamber length (from the injector flange to the nozzle exit) is 108.6 in. Cooling is accomplished by the circulation of engine fuel flow downward from the fuel manifold through 180 tubes and then upward through 360 tubes to the injector and by film cooling inside the combustion chamber.
This (which I found here) says 90 inches throat to exit. Two other items below show gimbal center to exit of 116 inches. So far I can not find the relationship between the throat and the gimbal center.
above: Throat to exit - 90 inches. found here.
above: Gimbal center to exit - 116 inches. See the "J-2S Side Drawing" link here.
above: Gimbal center to exit - 116 inches. See the "J-2 vs J-2S, McDonnell Phase B Shuttle Study" link here.