My 36 coupe had what looked like roofing tar applied in the inside of the car then applied 14g sheet steel over it all with rivots, must have taken a while to do.
Took out about 100lbs of sheet steel (what's that in stones?
) Then used a blow torch and a scraper. Days of fun.
I guess the only saving grace to it all was that the tar did a nice job preserving the original floors. Strange way to do floors.