I decided to use an original clock for my 1967 Impala SS. I bought an NOS one from eBay. I would have no problem using a used clock that was service/restored by a professional. The problem with original clocks is the contact/points burn as the car battery goes dead. I installed a hidden toggle switch to the clock power lead. I turn it on when I drive the car. If my battery goes low/dead because I did not put on the battery tender, no big deal because the switch is turned off.
