I realize that new or good used is the best option. But at 73, I am afraid the replacement job is beyond me. If I found good used trailing arms, what would shop time be? If subframe was removed, new mounts plus the trailing arm bushings would be needed. The rubber boots on the side shafts also look like they should be replaced soon.
My concern is that all this done by a shop might cost me more than a new car
Alternative is to patch as best as I can. Welding on a reinforcing plate, might be a stopgap measure, but to do that properly, presumably shock should come out and perhaps spring too?
Assuming I keep car and drive it as is, it will only be used as an around town car to get me to places like golf course or marina and shops. It would save me using my 72 350SL. For that, I will have to review just how bad the rust is. Maybe drill a few tiny holes. I wish I had a wall thickness meter like we had when I was working!