A tach pretty much just needs the switched 12V feed, a ground, the wire to power the light bulb in it, likely an orange wire to it and the sense wire out to the black/yellow wire on the coil neg primary terminal which is what the tach reads. Not sure if this OE type tach needs an additional sending unit or not but here is a BTT for ya. EDIT the diagrams at www.mymopar.com might show the tachs' connections MORE EDIT it shows a dark blue (switched 12V) & the sense wire, couldn't make out the color, looked like green/yellow but that don't sound right.