[tonythetarga]

I agree with Chuck, but you should also look at the sway bar bushings. You might disconnect the rear bar or remove it and see if the clunk goes away. The sway bar bushings are an easier replacement than the spring plates.
Another point I wanted to make is that the'bounce on the bumper' test doesn't work with these cars. The "spring" is a steel bar that twists (torsion bar) and the shock just dampens the recoil. Your 180 lbs won't do much as you found out.
If you choose to redo the spring plate bushings, do the front a-arm bushings up front at the same time, as well as both sway bar bushing sets. You'll be fresh and ready to go after the alignment and corner balance.