Are the oil temps doing the same thing?
If not, then I would do as above and make the coolant double pass if you can. Hard if the tanks are top and bottom, easy if they are on the side (which on a skyline they almost always aren't)
You could also try a lower flowing water pump. Flowing too fast causes cavitation and, therefore, higher surface tension of the water. A lower flowing pump in a car that revs much higher constantly can often be the only thing required to get those temps back down.
Or you could try an electric one