All RB flywheels have 6 bolts holding them to the crank - the difference is in the number of bolts holding the clutch cover (pressure plate) on. To quote Kudos Motorsport:
All R31/32/33 RB20/25/26 cranks use a 6 bolt flywheel to crank configuration, and the following pressure plate to flywheel:
•RB20E, RB20ET & RB20DE (225mm Clutch Disc) - 6 Bolt
•RB25DE & RB25DET (240mm Clutch Disc) - 9 Bolt
•R32 RB26DETT (240mm Clutch Disc) - 9 Bolt
•R33 RB26DETT (250mm Clutch Disc) - 9 Bolt