Hey mate, welcome.
As far as i know,only the Skyline GT-8 uses that transmission oil (KLE51-00004) no other skyline variants use it. I don't know much about 250 GTs, maybe someone else can help you out with it.
But a general rule of thumb i usually follow is that never to trust the odo. Service everything including tranny oil,engine and anything else as soon as you get the car.
Goodluck