I did, about 40 years ago. Iirc, there were some small folded-over tabs on the bezel/ring that had to be very gently unbent to release the lens.
Are you sure your tachometer lens is plastic and not glass, any I've seen from that era were glass - maybe try cleaning it?
Midwest-Bayless currently have an old tacho that they are selling as a source of the glass lens.
Al.
