Hi there, sorry you have had to wait so long for an answer. I believe ideally it's because of the difficulty behind this question in regards XXXXX XXXXX safety laws.
Ideally anytime you have floor pan or firewall rust through it's in the best interest to replace the panel. Keep in mind the flowo pan is only 2 pieces and the firewall a single unit. This can be more time consuming and costly thant it's worth to replace the entire thing.
You could certainly take another approach to this as long as you don't have vehicle inspections that need to be passed yearly. You could cut/weld an replacement portion from a salvaged vehicle or you could back brace it with a couple longer steel plates where the mounting holes would go, drilling your own holes. If the hole was excessive you could fiberglass over teh steel bracing for the pedal mounts.
theres certainly multiple options here depending on the severity of the rust and the restriction in your area.
Floor pan, forgive the typo.
I will simply this as much as possible for you, ask if you have further questions.
Ideally these pedal assemblies are part of a steel bracket, I am under the impression your referring to the floor/firewall area tha tthis bracket mounts to is rusted out? assuming that's the case, i was saying...
Assuming you don't have excessive rust over a large area, then you would be best cutting and welding in a 12" x 12" section. Just make sure to paint over your work area.
The steel bracing I was referring to would be indicative of a large repair area to avoid replacing the whole panel if it was cosmetically up to par.
You cannot order a small section of the panel, you need to visit a salvage yard or you will have to purchase the whole panel which is ALOT of work. i was merely giving you constructive alternatives to doing that.