Well, the only part that is Kyosho in that diff is the plastic housing and the screws... (and those have been replaced as well since the image was shot)
In the finished truck all old parts has been replaced or upgraded, except for the servo saver.
Putting a center diff in the Savage makes the rest of the drive train hold up pretty well, I had to do this modification already with 6s and the Lehner 2230 - the 2 and 3 speed gear boxes never lasted a full run.