Took out the interior and pulled out all the carpet to continue a little patching on the toeboards and see what was happening in the back. Pleasantly, after 47 years the back floors are pretty good. This is what I got after I took off the paint and some surface rust. However, the passenger side has a dent from the inside downward...like something had been dropped on the floor in the past. It's pushed down a half inch or so right where the strengthening ridges begin. Not sure if I should leave it alone or try to push it back up with a jack. I'm leaning towards pushing it up.

 

Interesting how strong the floors in these cars really are. I put a bottle jack under the floor and laid a triangle handled screwdriver on it to fit up into the angle of the floor ridge. The back of the car is up on jack stands and when I raised the bottle jack enough to push the ridge back in place it actually brought that side of the car up off the jack stand. Anyway, the dent is gone.