Upgrades for 325i What fits?

Hi,

Can anyone tell me what parts from the 87-91 325is (and or the e30 M) would bolt on to my 1991 325i. Of those components, what would be an upgrade and are they limited to wear and tear, i.e., Limited Slip Diff. would be nice but what if the 325is that it comes from had 250 000 miles? Any suggestions would be greatly appreciated.

Regards,

Jason
1991 325i (2-door)