Buy a used tach or new tach

The SunPro Super II tachs were not anything spectacular originally. Not sure if that was the one you are looking at or not.

Buy new.

unless you can get a used one that says it’s working for 1/3 price new.

I paid $5 for this one 25 years ago. Still work fine. Might pay $10 now. Have another with shiny chrome ring face. Might pay $15 now for that one.

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I have a couple myself. They were the cats meow back in the day. They always worked with any ignition