So describe your ignition system. If you are using the Blaster coil only, but still have points, the OEM style points tach will work. When I last had points I used the Mallory Promaster coil, the Mallory Super Condenser, [so big it mounted outside of the cap] and regular GM points. My old tach worked fine. When I started using the GM HEI was when I had problems with the tach.
