I can't see a $35 mech tach being worth the time to install it, plus needing to figure out a drive for it. If you do it, probably need a generator from a Bugeye Sprite, they drove tach from rear of generator. Being a 1962, I would have expected it to be mech originally.
Can't recall the name, but there is a repair place in Albequerque that I used years ago, might check with them