I'm pretty sure the Buicks never had the emblem put on from factory, but I'm pretty sure they were placed on the left side along the corner of the decklid with the other makes that had them. If you looked at the trunk lid of a '70 GS and noticed where the GS is placed, it'll be placed on the opposite side at the bottom left side corner of the deck lid.
The only 69 I know that had "hurst equipped" badges was Jimmy's 69 Motion GS. His has one on the trunk lid and another stuck in the dash. Duane