Looking at the pica again, looks like my previous post won't be the perfect fix, but it should get you through....

This very common on 2nd generation Camaros due to a leaking windshield. It is a pretty easy fix to cut it out and reweld in a patch. You may need to have someone with a welder do it for you but it isn't that difficult or expensive.
You do, however, need to figure out where the water is coming from.

Jeez man, i'm afraid to even look at mine now. I shovel all winter for work and i'm in and out with slushy boots. Was that the cause of the smell you mentioned?

Cut out all the rust, get some sheet metal, shape it as close as possible, sand all the surrouding metal down to bare metal, etch coat the metal, weld it in, a mig welder should be allright, after its finished get etch primer and primer up the location, then I would use under coating on the bottom side and just regular flat black paint on the inside. If the floor boards are really rusted all over the place scrap the car.

"'Tis but a minor flesh wound!! Stand up and fight like a man!!" /british accent :P

Sorry, reminded me of that, heheh. I actually agree with Trofeo on this one. Time to let 'er go. Like I've mentioned to you before, you have a rare troublesome Bonnie there. Go find a black SSEi.

I agree, I think that is fixable. I realize how bad that must make you feel, but I think with the money you have invested in the car (the powertrain is solid, right?) you should give it a shot. If you can't weld, have someone do it for you.

The real question is WHY that is happening...that is not a common occurrence on Bonnevilles is it?

That'* just it. The powertrain isn't solid. Still having back-firing problems and such after replacing numerous things like the cat, etc.

what does the passenger side look like?

I've never seen something like that happen before! I thought the floorpanels on the Bonneville were galvanized steel?

Well, his leaking door seals are what probably contributed a great deal to that. I hate to say this, but you better check the back floorboards, too, since you have extensive leaking around your back doors too. :?