Larry,
The frame, or birdcage, is shaped to fit under and support the body and welded in place, unlike the aluminum body frame which is attached to the body when you receive it. Then, the fiberglass body simply sets on top of the birdcage and is bolted to the chassis outrigger tubes at the bottom on each side and in the front below the
oil cooler.
If you can't find pics of an original style chassis for fiberglass body, check out the Factory Five chassis. Pretty much the same bird cage support system.
Bob