[VetteVet]

The SI alternators ground through the case to the engine block so the internal regulator is automatically grounded. The old style regulators had to be grounded to the sheet metal and to the alternator bodies in order for the points inside the regulator to work. While it won't hurt anything to have the ground, it isn't necessary.

You do know how to set up the drain check where you disconnect the negative battery cable and connect a test light or multimeter between the battery terminal and the negative cable? If you have a light, or read more than .004/4 milliamps. you have a drain.

You want to check all the key off stuff first, so disconnect the alternator, the horn relay, look for any lights on. Stereo amp or radio etc. Don't forget that older batteries can go bad internally