My friends S14 locks up the fronts really quickly (and way before the rears) with 300zx brakes. I think a proper proportioning valve will go a long way. I get fade very very quickly on my S13 so I will probably go to Z32 brakes soon.
I ran a quick little road by my place and in 15 minutes my pedal was almost to the floor. I wasn't even running hard either (never took it above 4k rpm, because it was raining
)