blown77z also shared this bit of info with me. for some nice urethane bushings that fit perfectly in the q45 diff, order energy suspension part # 7.1108G [for the 90-96 300zx] and use the front diff mounts only, either sell, keep or toss the rear mounts it comes with.
i ordered mine thru autozone [i think $24-was less than anywhere else] and pulled the diff to do the install this weekend.
once the diff was out, i followed the directions from the energy sus kit. you remove the rubber from the large dome shaped washers and reuse them. then remove the stock rubber bushings. i used a hammer and large socket to drive the bushings [steel center, surrounded by rubber then steel outer] from the diff. pretty straight forward. tapped in the new bushings and reinstalled the diff.
looks like they'll work great. thought about pics but as it was pretty simple...i did not.
plus, the directions are easy to follow.