Any thought on this? It looks like the rear is completely torn up behind the seats!
https://www.hemmings.com/classifieds/dealer/bmw/3-0cs/2153133.html
Completely redoing the rear parcel shelf is a relatively easy project. What should be more worrisome is the installation of a massive stereo system below that shelf in the trunk. In addition to the usual inspection for rust and mechanical condition you would do on any e9, look carefully at the stereo install.
In my car, the massive stereo system was wired through fuse number one. The clown who installed it pulled the five amp fuse and installed a forty amp fuse in its place. Thus, when the owner blasted her tunes, the fuse block melted at the site of fuse number one. And when she used the lights and/or blinkers while blasting her tunes, the wiring for the lights melted near the fuse block, and the plastic surrounding the bulb holders along with the wiring near the lights melted, both in the front and rear of the car. There is no cookbook for fixing this type of damage; you need to apply a basic understanding of electrical circuits, test, repair and test again. And much of this work is done underneath the dash with the floor sill jabbing you in the back. It is a pain in the ass if you do it yourself, and I suspect it would have cost at least $5k to pay a professional to fix my car.