I just looked at the photos of the car on the rotisserie., if you have that much rust thru in the foot well area I would be willing to bet you have if not thru holes at the least thin metal on the fire wall area by the foot well. I did a few small patches and had to replicate the ribs in parallel on the pass side with new metal. I'll see if I have pics of that too. Hopefully your torque boxes are in good shape.
I also had some areas where the floor was rotted between the brace and rocker on the driver side.
The front fire wall connections and torque box look fine so far but I expect to find some holes in the inner rockers where the braces and floor are pinched welded.
Where did you get your floor pan? Dynacorn, Goodmark?
Engine Test Stand Playlist: https://www.youtube.com/playlist?list=PLwoxyUwptUcdqEb-o2ArqyiUaHW0G_C88 restoring my 1968 Firebird 400 HO convertible (Firedawg) 1965 Pontiac Catalina Safari Wagon 389 TriPower (Catwagon) 1999 JD AWS LX Lawn tractor 17hp (my daily driver) 2006 Sequoia 2017 Murano (wife's car) 202? Electric car 203? 68 Firebird /w electric engine 2007 Bayliner 175 runabout /w 3.0L Mercuiser__________________________________________________________