He usually recommends Bilstein non adjustables. See here for a useful discussion:
http://www.skylinesaustralia.com/forums/topic/374385-bilstein-coilover-conversion/
Depending on what you want to do affects spring rates. 5/4 kg/mm front & rear tends to be a bit soft for the track. I ended up 5.5/5 which with the attessa controller some sway bars, much -ve camber on the front and other bits works well. From what I can remember from Bilstein themselves the standard offering doesnt need revalving in that range.
From Bilstein:
The front shocks, if they are as per factory spec, will support a spring rate of about 10kg/mm. While the rear, again at factory spec, will support about a 6kg/mm spring.