Restoration Commence.

Cool, another heirloom and another '73 resto. Paint (and rust) looks a lot like mine before I buffed it. Not a lot of paint on those '73s.

You are going to want to use the Ospho on non- finish painted surfaces (think floorboards, chassis, etc) and strip that rust abrasively. The way rust pits the surface, it's a big risk that it will bubble later. My Beetle painted 8 years ago is proof.