Unfortunately I didn't look close enough at the floors when I purchased my E-Type Jaguar.  A silly mistake I know, but I had lifted the carpets and at first glance everything seemed OK.  Someone had "dummied up" the area to hide the rust and holes and it was only after three months of ownership and a more thorough inspection that I realised the extent of the problem.  The floors had to be replaced!

Photo Gallery - Rusty floor replacement