thanks a ton for the valuable advise. the s30 is a whole new game for me, unlike my s14.
now that i know that poly and slid bushings do exist, i'll probably go with the poly ones, just due the fact that i'm not building a full-out racecar. i'd like to preserve the car's structure and frame as well, and think that poly bushings would be easier on it rather than the solid aluminum ones.
since you asked about the z31 LSD, i'm assuming its a direct swap?
edit:
http://www.thezstore.com/page/TZS/PROD/PSDC06D/23-4139 <-- is this the correct kit that would replace the bushings in question?