You can use Captain Lee's Auto Spray Strip on a Corvette of that vintage.
It removes the paint but not the primer. So, it doesn't damage the fiberglass since it never touches it.
The primer can then be sanded off which is much easier than sanding off paint.
I used Captain Lee's on a '69 recently that had original paint and it works good. But, it is still a gooey, messy job. I would do it again however.