question about front valance?

You have the right setup. There is no difference in the shape of the valance from a Cobra and any other II, just cutouts on the ends which don't affect chin spoiler installation.

The fiberglass may not fit 100% perfect, but should be fine. It will be a bit snug on the ends that bolt to the fenders.
Just guessing, I'd say the problem is the way you're trying to line it up. The holes in the valance start to recede as they move away from the center.

As for spacing, there are indentations in the fiberglass spoiler where the holes are to be drilled (except the center hole). Measure these, and also lay the valance upside down and mark off from the straight back part of the valance 4-1/8, 5-1/8, 5-1/4, 5-3/4, 5-1/4, 5-1/8, 4-1/8 (end to end).

That's 7 holes in all for the valance, plus 1 in each fender.
Good luck!