At least on the 68, there are a number of studs going through from the dash pad. You need to take the nuts off from under the dash. The leftmost one is difficult to get to without removing the instruments cluster but I think you might be able to to it with a flex drive.
On the 69, there are four studs along the back holding the pad down.
those are the ones the OER replacement (at least few yrs ago)did not have attached to a steel backing in the dash(dont have still ??) and it dimples there where yoiu attach it.
