I'll peel the carpet and seal holes to keep my feet dry when taking water crossings, but I imagine the truck will outlive me whether I correct the rust or not. The post above is great, but most times people rip the entire interior out, cut large chunks out of the floor, give up, and eventually sell it for a fraction of what they paid, which I would often still consider to be too much.
Seen it enough times and declined to pay over $250 more than once.