Don't know what it was like back then, but these days, a flood car (one that has been under water above the rockers) that is less then 10 years old at the time of going under water, can not be "rebuilt" it has to be scrapped.
I suspect that back in those days, a new interior, and a different drive train and they could sell a car that would have strange odors on hot days and would rot away in a few short years.

Having been involved with the rebuild of an older car that was under water a total of 4 days (flash flood) means pretty much everything needs to be rebuilt or replaced. If the interior can be removed and the body can get washed well enough to get the water born bacteria out of it, it can be saved, but its not something for the weak at heart.