Trying to wire the classic instruments 5 gauge set for 65/66 mustang. Says to connect to 2 wires on the speedometer calibration button. Anyone know where said button might be? There's 2 knobs inside the speedo but they don't seem to have loose wires and I don't want to put a hook in there and start pulling. The instructions don't have an illustration showing where it is. They're closed on the weekend so I can't call tech support until Monday