I spent most of the seventies working as technician in NYC. My practice consisted mainly of S&S grands in institutional and professional settings.
I, personally would not recomend an instrument from that era with teflon bushings. I made a fair amount of my income dealing with the issues (mainly clicking) connected with these bushings.
Regulating these bushings involves a completely different manual skill and different tools than the usual felt bushings. The skill is not particularly difficult to learn but requires a certain amount of practice to really get it just right. Many techs in the field just haven't come across enough of these instruments to really develop that skill.
When properly regulated, the bushings work fine for a while (sometimes if your lucky, quite a while) but they will usually develop problems eventually. The larger bushings introduced in the 70s were an improvement, but the basic idea was fundamentally flawed IMO.
In addition, IMO there were a number quality control problems during that period. I would recommend that anyone considering an instrument of that vintage to have it examined by an independant (and hopefully unbiased) tech or rebuilder.
All that said, most of these instruments have outstanding tonal characteristics that can be brought out by careful attention by the right technician. It may very well be worth replacing the action in them. The Franz M. and his staff regularly performed what I considered to be minor (and a few major) miracles in those days.
BTW, I've been out ot the business for about 20 years and have not seen a new S&S in that time. I've heard that quality has improved somewhat but cannot say from personal experience.