As written up in the genuine parts manuals

HQ
NUT - WHEEL Hub Bolt
NUT ..................... Rally Type Wheel ..............2825904......20

HJ
NUT - WHEEL Hub Bolt
NUT ..................... Rally Type Wheel ..............2825904......20

HX
NUT - WHEEL Hub Bolt
NUT ..................... Rally, Polycast Type Wheel ..............9939942......20

HZ
NUT - WHEEL Hub Bolt
NUT ..................... Rally, Polycast Type Wheel ..............9939942......20

Interestingly the diagrams HQ to HZ all show the black cap version.