I fitted what I was told was a clutch / flywheel assembly for a RB20 onto the back of a RB25 and slotted the engine into an R32 (GTS4), still with std 'box.
It was an Extreme / Exedy HD pressure plate and, I think, a ceramic spring-centre driven plate. It is "heavier" than a standard setup, and has been handling 180 AwkW.