Most if not all cars using a fiberglas top are attaching the top to new mounting points welded on the roll cage. It just depends what those mounting points are. Mine are just threaded holes for small bolts, at the end of little stubs that stick out from the cage. I've seen one or two using DZUS fasteners.
On a stock car, it would be a whole different task! There are no suitable attachment points at the ready. I'm not aware of any kit that would adapt the stock front latch and rear spin locks to something that would reach to a shell. I don't think the center latch in front would be sufficient given the flexibility of a fiberglas top at the front corners. And on the sides, the spin lock hole is quite a distance from the shell.
Here's a photo of my car just after the cage was installed, which shows the mounting points pretty well (one on each side, and three along the front). There are corresponding holes in the fiberglas top, and little bolts that screw in.
