I have that exact set up on my '64 C20. Most current tach's out there have a setting for either 4,6 or 8 cylinders. You may have to take the back of the housing off to find where you make that adjustment. It is easy to hook up on the HEI because there is a connecter already there marked "tach". It is there with the rest of the wires plug into the cap. You just have to connect the signal wire (the one that would normally go to the coil) to the connector. It works slick. Good luck!