About to do a swap, need dif help please

[RCV7]

I'm a noob so please bare with me. I have a stock '96 Ti active. I"m about to purchase a Z3 2.8 engine and a ZF trans from an M3 complete with clutch and drive shaft. I gather I can't use either difs from my ti or the donor M3. I'm Looking to get an LSD dif.
1. Can I use a Z3 6 cylinder dif and if so which ratio would be best and easiest to bolt up? I'll be using both 16 and 17 inch rims with low profile tires.
2. What kind of gearing would a 3.15 from a Z3 give me with this setup?
3. Should my hybrid drive shaft be from my existing ti and an M3, 328 or Z3? I really don't want high rpms at speed or the opposite. This will be my dd as well as autox and some track. Your thoughts are appreciated. Thanks in advance.