I believe that on the 51-3 cars, the steering shaft (long rod from the box to the steering wheel) is an assembly that is removed from the car with the box attached. You'll then need to disassemble the steering box to get the shaft out. On the 54s, a vibration damper was used in line with the shaft so to remove the box without having to take the rest off the car, one needs to just disassemble the damper.