Z3s are four bolt pinions (or input shafts). These diffs are the mid-size diff case which is the same as the E30. You'll need the half shafts as well and the ABS sensors will need to be shimmed.
The diff is a direct bolt in for a TI with the correct halfshafts. Early TI models will require some customation to the hatch floor support to fit the diff. Later models came from the factory with the necessary modifications to accept the diff.
My personal experience:
1995ti - had to be modified.
1998ti - direct bolt in.
Again, both require E30/Z3 half shafts. __________________
SOLD!!! 1999 332ti //M Sport Titanium Silver
M3 S52 3.2 I-6 Engine, M3 Clutch w/ ti Getrag Trans, Z3 3.15 LSD medium case diff and half shafts, OEM Hatch Spoiler, Eurosport HP Underdrive Pulleys, FDM, 17" DS1 rims, M3 Front Struts & Springs, M3 Instrument Cluster, 3-spoke //M steering wheel with tri-color stitching, SSK, CCFL Angels in Depo projectors with 5k HIDs | 
Z3 LSD 
Hybrid Mode
