Then it was discovered that if bumped the hose could come out of the floor so they added the clamp and screw.
Marty
This might explain how the ONLY thing rusty at all on any of my floorboards is the inside of the passengers side, pretty much everywhere below this hole. Recommendations for "best repair technique" will be brought up after removing the rust to see how bad it really is. (at a glance, only a small slit is rusted through, about the size of the tip of a butter knife)
Once the surface rust is gone, I'll start that thread or look for ideas in other ones. If anyone could steer me towards such a thread, that would help. The bottom side of the floorpan still looks really well, so I am hoping the rust isn't too deep everywhere.
A side note: I believe I am more likely the 2nd owner.(not 3rd, though I have no previous owner records & haven't been able to find any) I bought it in early 1978 and at that time I am sure it was completely unmolested anywhere I looked. (and I looked everywhere) I wasn't a rookie working on Mustangs at the time and could easily spot cars that had been tampered. This aspect was the sole reason I chose to keep this car as a life-project, that is, since the paint, interior, engine, transmission, suspension, & all were completely original at that time. I say this only for clarity over any of the things I discover.
Richard