For the G25M-R: G565-27-190A (4.105 ring gear ratio)
     For all F25M-R (I doubt it will fit an F5M-R, you're on your own if you do!):
     4.105 ring gear ratio: F046-27-190B
     4.388 ring gear ratio: F045-27-190B
     The F25M-R viscous LSD will also work with 3rd generations.

     MazdaSpeed also used to have 1.5 way  LSDs for the G25M-R and F25M-R
     transmissions.
     The part numbers are:
       9B1A-79-960 G25M-R 1.5 way LSD
       9B2A-79-960 F25M-R 1.5 way LSD

     NOTE: straight forward "bolt on" installation can ONLY be done if you DO NOT
     change the final drive ratio of your transaxle. If you choose to change the final drive
     ratio, you MUST change the pinion gear that is pressed onto the counter shaft of
     the transaxle. The appropriate pinion gear can be sourced from another F25M-R
     that has the final drive ratio you want. In Mazda transaxles, the pinion gear is
     machined into the counter shaft, therefore all counter gears must be pressed out
     and pressed into the replacement shaft.

     For the counter shaft that has the:
     4.105 ring gear: F5D3-17-301
     4.388 ring gear: F5D4-17-301