My 1987 Buick Regal has a rear molding piece at the top of the rear windshield that won't come off after taking out the screws and gently prying it. It slides back and forth a little but won't come off.

These type of GM cars has a clip like the one below - they are V shaped and fit into a slot that is a little narrower than the 2 wings on the clip. Hence making it very hard to pry them out without breaking them. If you have the rear trim that attaches in the center with a small plastic piece with a single screw in it - you can remove the small trim piece and slide the trim off the clips. If it is a solid piece along the rear glass, you may wind up breaking one of them, or even 2. But as long as you have one for the center, with the 2 screws on the end, you should be fine. We carry this type of clip, you can find it by going to the trim plug and clips category - it will fit all GM model cars with this type of clip from 1980 through 1989.