From your pictures, it appears that your car has separate sail panels. Your headliner goes down as far as that horizontal metal bar which should have cardboard in the center to staple or tack to. The sail panel is held in place with panel clips to cover the rest of that area. The rear of the sail panel is open, and the fabric is glued around the rear window opening. There are still two panel clips sticking out on the driver and passenger side sail panel area, just below the horizontal metal strip. I did a '69 Camaro a couple months ago that was the same way. I can't see any way to attach windlace around that edge next to the rear side windows. That has me stumped. It almost looks like there should be some rubber trim or something like it there.
You're going to have to find a Chevelle that has a headliner in it and take some more pictures.
I did some internet checking, here are the sail panel blanks: