sincitylocal
+1y
Yes, it can be done to the factory tach.
I did have a thread on Mazdatruckin about it.
You need to go to pick-a-part and get a tach from an 82-92 Camaro or Firebird.
V6 or V8 donor specific to your need.
You only need the electronic portion of the tach, so take it out before you pay for it, so it'll be cheaper.
I'll see if I can put another thread together here to make it easy for you.