[bigblockv6]

According to the GMC literature screw on U shape clips were supplied with the clock for installation from the back, furthermore mounting it from the back makes the gauge blend in with the rest of the gauges and not look like an add on. As far as being a dealer installed accessory that's not quite true. My fathers 62 K1000 came equipped with the clock from the factory but upon delivery of the truck he requested they add the corresponding gauge to left side of the cluster which was a Bat-O-Meter, it too was installed from the back side.