Fiberglass floor pan removal for body mounts

[75ranger]

Hey all-

I am looking to replace my body mounts but just thought of a huge obstacle. The PO, in his infinite wisdom, decided to protect the floor pans but fiberglassing over them. They actually look pretty good from the underside so I am not sure exactly why he did it. Aside from trying to get lucky and drilling through it to get to the bolt head, are there any ways you guys can think of to get this done. I want to get my panels lined up before I think about a respray.

Thanks