I am not a fan of bolt-on spacers, especially if the vehicle is tracked. Our sanctioning body prohibts their use in favour of extended wheel studs.
Check the feedback from the OZ forum below as a "for instance". Simplest and easiest to use longer studs ... ARP sell them and whilst it is a pest to install them (or costs a few bucks to have a shop do it), better all round to use extended studs.
Web reference here:
IMPORTANT ADVICE: Don't run spacers! - Brakes & Suspension - Zclub - Australia's Largest Nissan 370Z and Nissan 350Z Forum
Hopefully you can see the web reference as a guest .... if not, let me know and I'll cut/paste into this thread ....
RB