Here at XAT, we exclusively use Wilwood master cylinders for all our conversion kits.
If you are using an XAT clutch adapter kit or transmission adapter kit, you will need the 3/4" size
This is what is needed for converting the Crown (JZS155, JZS151, etc.), Chaser/Mark II/Cresta (X90, X100, etc.), using our LHD UCF10 LS400 clutch pedal bracket, etc. where firewall height is an issue.
Wilwood’s Compact Remote Combination Master Cylinder, commonly called “shorty” master cylinder; only 3.375” long, is about the size of a roll of quarters. It’s available in bore sizes from 5/8" to 1.125”, and with or without reservoirs.