Best thing about original Biopace was the rings wore out real quick, maybe one third the life of a regular ring. For the OP this may be a problem, as he will be seeking service parts not made in thirty years. Plus Shimano was and is always awful at supplying service parts, there never were inventories except as OEM.
Can’t follow the discussion about efficient pedal speed. All of us pedal at different speeds at different times. Mountain biking would sort of define doing lots of different things with the bike. All of the old studies about 60rpm were done with casual riders or non-riders.