Several years ago I bought a 56 Ford that the previous owner had repaired with soft aluminum formed to fit the floor and then pop riveted it in. Actually, it wasn't too bad of a fix. However, I didn't like knowing it was there and seeing the pop rivets from the bottom side of the car. I cut out the old rusted out area with a plasma cutter and plug welded repair panels in and then put a small bead along the edges. With a carpet, it appears to be like new.
