If you're running a 12 volt, negative ground electrical system, you've got a bunch of options. Original 6-volt systems, or any system with positive ground narrows the field a bunch. Check out the JEGS catalog, or possibly PAW, and you'll find a wide variety of designs and prices.
Just pick one that fits the mounting position you want, and be sure it has a 4-6-8 cylinder selection capability. Most tachs will have at least 4 wires, (+) and (-) power connections, a trigger lead that goes to the distributor, and a wire that attaches to the dash light circuit for illumination. Some of the high-end tachs will include circuitry for rev limiters, shift lights, etc. Unless you're racing, those features aren't necessary.
Jerry
