I am sure the channels should be lined with felt or a felt like material, after 40-50 years it wears thin and the window rattles, the nylon slides help as well, but the felt is there to keep it from rattling around.
I just got done doing my triumph, I had had a similar car in the past and it had rattly windows, which I hated. So swore I wouldn't have it again, I put in new slides and made sure everything was tight and adjusted in the mechanism and I have quiet doors. I know not exactly the same car, but principles and fixes are the same.
Quiet doors are a good thing, working on them is a pain, as you have to take off the panels, and you have limited access in there, and of course you don't want to break the glass, and of course you want to mske sure it is all going to stay in track etc. before you put it back together so you don't have to do it all over again.
But if it is bad and bothers you probably worth the effort.