hey shahano,
yeah, i am still building diffs... in the meanwhile it became my main profession (i built ~1.500 diffs to date.
)
for the 1M, your application and your experience/skills i would install a slightly longer FD and a drexler gt race light lsd core (i will suggest a detailled setup with according locking rates and preload during the order process).
you will not become happy with the OEM lsd type. so i would suggest to upgrade to a clutch type unit... and simply take the best, as BMW does for their factory GT racecars!
if you are interested feel free to email me:
service@limitedslip.de