I'm digging further and finding that I will need to replace the floor pans or at least most of it. It looks like the rust problem was caused by the fact that water got up from the bottom and then underneath that rubbery coating. That coating kinda looks like a heavy duty roofing membrane. You can see pieces of it ripped up in the photo. I suppose that this stuff was put in at the factory since its painted 918. Was this put in to be a noise dampener/insulation? Odd that there are drain holes that actually served as a way for water to get up under that coating.