I got some answers back from Mori San at KEW.
Their crank damper is a fluid filled item. The 43,900 yen race crank pulley is compatible with standard water and alternator pulleys. The pulley on this item is 102mm O.D.
The 70,000 yen 'race crank pulley kit' is only compatible with the water pump and alternator pulleys which are included in the kit with a different belt to suit as well.