Apologies ddk632 & PiK as I hadn't seen your posts until I received a PM a day ago.
Likely you've found other info but I'll add that the Auto Solutions SSK really does transform the shift precision/feel. It being a complete linkage unit from shift lever to transmission coupler with hand assembled bronze bushings (& thus perfect tolerances) I doubt any other SSK can compare, it's definitely worth the $.
Here's a link to a good thread in the M2C section with many user reviews (our OG cars of course have identical clutch/trans/shift linkages).
https://f87.bimmerpost.com/forums/sh....php?t=1643086