The S110 SX is an early silvia luxury???? model. The calipers are steel but small and light.
If you are using 4 pots up front the front, rear bias ratio may be a problem without a balance bar setup.
The S110 piston sizes are small as is the pad area.

I think my rears are only doing 10% of my braking any way. I have Nismo Dunlop MK63 calipers and 253 mm discs on the front with balance bar (intermitently).

I was using R31 skyline discs on the rear but went back to air scoop fed ventilated drums (2" holes cut in the mounting face) when I put the car back on the road as a daily parts pick up mobile.