From an OEM Part Number point of view, none of the clutch part numbers are the same as an FC RX-7.
Having said that it is quite possibly they look identical, but, the only difference is perhaps clutch plate compound material, number of rivets, or pressure plate spring strength.
Just remember the RX-8 has a higher maximum RPM engine when compared to the FC.
2009 Series 2 RX-8 CWP 6MT
2011 NC2 MX-5 6MT