The original factory tachometer was a rare option in the Mustang and when equipped with this option Ford eliminated both the oil pressure and the alternator gauge to make room for it and replaced them with warning lamps. This mini tach is a great way to add a factory-looking tachometer to your instrument cluster without sacrificing the other gauges. This tachometer easily installs in an optional clock hole and provides an OEM appearance. Works with both 6 & 8-cylinder engines via dip switches on the back side of the gauge. Dip switch settings: #1 switch up, #2 switch down = 8cyl engines #1 switch down, #2 switch up = 6cyl engines