Hi Welcome to the forums! Looks like your typical black tank rust out with a bit of fiberglass moisture rust. So what to do? What to do! There are alot of different ways to do it Shell on/off, frame repair as needed, Por15 (or another type of rust preventing paint), and then the floor. Soo much debate on that damn floor! My suggestion is read on. Everyone has an opinion about how to go about it. I went with Aquateck MGP in the 15mm (5/8in) I am going to epoxy the edges with West Systems Epoxy then Spar Varnish the rest. It is not cheep. I would rather spend the $$ on this part because it is a big part of the support. But do what you gotta do, cant wait to see more progress. Such a great couple project! Good luck!