nerfhat.... Buy the whole kit and do the car right. It's much better to not mix old worn out bushings with new ones. You'll find the car will handle so much better when you replace the front ones also.
http://store.summitracing.com/egnsearch.asp?SearchType=Make&N=700+4294907666+4294906934+4294925061+4294925130+400008+115+4294865789
Rumnhammer.. If you have not, retighten all your bolts in the rear and check the two bolts on the mustache bar. If they are loose the bar will move and make that clunking sound.
LARRY