well i doubt the ae71/86 /t-18 pedal box would fit but you could test fit and see how close it is. other wise you'd be looking at a custom pedal box mounted with a standard rolla clutch MC and custom line to a s13 slave cylinder.
depending on cash and skills you can make one up yourself. pay someone to make one, or throw a tilton pedal box in
but have a look on rolla club i know theres a few heavily modded ke's on that site.
-dan