Vintage Thorens turntables from the 70s typically have flimsy and thin wooden bottom boards. Four small rubber feet are screwed to the plinth through the bottom board.
Some prefer to keep board and feet as they are to preserve the original look. The bottom board can be easily dampened with a properly sized bituminous felt sheet. I’m also for preserving the original look, but I feel the turntable would be better without any bottom cover than with that thin, resonant, cheap wood rectangle. An open bottom plinth would also allow an easier access to suspension springs for adjustments. Any way, dampening the original bottom board is an easy and effective tweak for these decks.
I also believe that better, bigger isolating feet would do a great job for the wooden plinth. Spikes could also be used, but I have the feeling the old Thorens are already well isolated from external vibrations thanks to their suspension system; maybe larger feet with rubber at the bottom and some dampening material inside them would do a better job. Usually I order the feet from a dealer who offers some color choices: black, gold or silver. I like black for lesser turntables like the TD-165 and silver for TD-160s, but it is just a matter of taste.