To insure good tachometer operation, you should replace the entire tachometer cable assembly. This cable is the 356C version with sound dampening rubber sheathing under the dashboard area. Also, the cable has a protective braided metal casing where it goes under the valve cover and near the exhaust pipe.

Note: This cable with the sheathing is the only one in current production. For concour prepared cars, the sheathing may be cut off, leaving the original bare cable.