While driving and going over bumps, I notice a very light squeak/clunk behind me towards centerline, right -side. I am sure it reflects an aging rubber joint somewhere, which one? Struts?. The car has 40K miles.

 

There are other possibilitys but it's likely that what your describing is a result of one or more bad pillow-ball bushings in the rear suspension. Pretty common and not really difficult... but the bushings are a little pricey. Mine were noisey @ 53k when I bought my car.
https://www.rx7club.com/showthread.p...ht=Pillow+ball