There are 3 pins in the grip frame. One is a flush cut trigger reset spring pivot pin - a solid piece of pin-stock at the rear of the trigger guard, one is the trigger spring retainer pin - a splined pin with a turned head on each end at the top of the grip frame backstrap, and one is the grip locator pin - a roll pin at the toe of the grip frame.

The grip locator pin is what you're talking about.

You don't necessarily NEED the locator pin on the Super Blackhawks with the Pachmayr grips, since the grips wrap around grip frame, but it does help keep them from wallering around a bit. If the locator pin holes in the grips aren't deep enough, you can either file some length off of the locator pin or drill the grips a bit deeper.