1966 Barracuda Formula S tacho wiring

I had that’s same car and it’s likely your tach that quit. Only wire I remember off hand is grey to the negative side of the coil.

Regardless contact or google ‘ rt-eng ‘ and ‘ 66 barracuda tach ‘ and you’ll find some good info there. They make a replacement digital tach to go inside the original housing (which I think was tucked under the drivers side lower kick panel?

Where in Aussie?

Good luck