Probably would depend on which conversion kit is being used.
I think I still have my S15 OE dual mass kicking about, if you want it for free+£post let me know and I'l try to find it, S14 clutch works fine with S15 flywheels.
If you want a new one, Driftworks sell S15 single mass conversion flywheels with bolts for about £250iirc