1966 OEM original cl not mine!

[factorystock]

I don't know about mice, but I have seen this area rust because of the drainage holes being plugged up. When water puddles in this area for a long time it begins to erode the metal under the factory caulking. Water and moisture begins to rust everything under this area all the way down to the bottom of fenders and rockers.But more common on the '60-'63 era than the '64-'66 era.