I am in for some more T60 and T48. Yes, it fits DSN case Ti.
As for the stem, actually ETA/Asian 7750 can be fitted with 1.2mm stem too (it comes with 2 sizes from ETA). But ALL Asian 7750 based reps that I have seen all comes with 0.9mm stem. Yes, you need new stem for most of the case (I have fitted on a few PAM auto and manual wind, all need new stem). Unless you want to glue to stem thread to the crown to adjust the length, then you need new stem.