Its the G25MR. The only "real" LSDs available are the Quaiffe and Mazdaspeed LSDs but they are setup for 28 spline axles instead of our 26 spline. (the Quaiffe is also known to explode, and I have seen the MS lsd fail too)
The Probe is a 28 spline axle. You'd have to get a set of custom axles made or use a Probe inner CV cup and a Kia intermediate shaft.
However MFactory is in the final stages of testing their purpose-built LSD, which is going to be engineered for both 26 and 28 spline axles. Its a helical gear type LSD, capable of holding 900+ HP, and has a reasonable price tag of $650USD. Comes with a lifetime warranty too!
It should hit final production within the next month or so. Definately worth waiting for.
http://www.teammfactory.com/products.php?category=Helical%20LSD&mod=MZ