My '67 coupe uses a long piece from the front lower corner of the door (near your feet) all the wall up and back to where the roof meets the quarter panel, and pinches the headliner in place. It tucks just under the sill plate in the front.
There's a short peice at the rear door opening that tucks under the sill place in the rear up to the beltline, and pinches the interior quarter trim to the quarter panel.