On a 68 it is the front hole as in the picture. I believe the 70 uses the rear one. I have a aftermarket inner fender on the passengers side and there is a dimple that was is not drilled.
Anywho I know for sure 68 is the front one and I believe the larger rear one is for a 70 up. Excuse the mess now that you made me look there is buffing compound splattered everywhere in there.