This might help somewhat....generally when I install 70/1 Cuda tail trim, if no holes are present, I'll tape the moulding on to the car untill it sits right, then using some 1/4" or 1/8" masking tape, tape around the outside and inside perimeter of the trim as it sits taped to the car's panel, then remove the trim, and mark out the holes in the center of the two tape lines, and space accordingly along the panel, incase you've never installed the plastic clips that come with the trim, you drill a hole just big enough for the clips barb to pass through the panel, the clip sits flush with the panel, you then tap the plastic pin located in the center of the clip flush, this spreads out the clip's barbs, just make sure the clips are nice and straight, the corners use wire style retaining clips, depending on whose trim you have, they could be push in type, threaded, or speed nut...
Mike