I rebuilt my tach following these instructions.
https://sunbeamalpine.org/wp-content/uploads/2017/10/alpine_tach_repair_rev5.pdf
If you are handy with a soldering iron, give it a try. I bought the parts from Digikey.com.
It seems to work without modification with a Pertronix 1281. Some calibration with the adjustment pot was required. For me, the instructions were excellent.
A little finicky, but fun to do. I just installed the electronics to get my clock to work. And it does. Another battle concquered.