We installed a tach on our 1996 MH with the 454 CID motor and as I recall it connected to the distributor, to 12v power, and to ground. There should be instructions with the tach you buy. Be sure to make a good ground connection, perhaps using a star washer. Once our ground wire came loose and the tach needle jumped all over the place. Re-tightning and using a star washer fixed it.