However, on the forward (leading) ends of both lower trailing arms, I have this situation:

Note that this is *after* several minutes with a small wire wheel AND 50 grit sanding drum. I was able to chip some off with a 1/4 inch cold chisel, but not much. Almost looks like metal melted into the socket. Or...eroded out of the socket, given the age of the car. Both upper trailing arms cleaned up nicely, as did the panhard rod.
I guess I should also add that all four trailing arms and the panhard rod do a nice imitation of a rain stick when tilted back and forth. Not heavy sound of rust particles, but clearly audible. Do these sound like items due for replacement? Rather not have impromptu rear axle steering if I can help it....

Thanks.
Neil