The correct torque is 350ft/lb or 45kg/m. However that's not the full story.
Wheel nuts should be tightened with the weight off the wheels, after the mating surfaces and been cleaned and smeared with a smidgen of anti-corrosion grease. I use copperslip but understand there is an silver grease from Castrol forgotten the name, that is even bette.
Once nuts are tight they should be undone a quarter turn and then retightened to 350ft/lb. Only at this point should grub screw be inserted. It is also important to ensure that the grub stress lines up properly with the castellation.
These Oz wheels have caused quite a few problems over the years and a lot of discussion? However used properly they are, in my mind, a great feature of the car.
