Well after quite a while I finally got around to ripping out the carpet (original) in my 67 Mustang. And as you might expect it’s rusted through. Ford never intended the mustang to last more than 5 years, 10 tops and as a result when they built they didn’t really pay much attention to things like primer and sealer and anti-rust etc. Not that the industry paid a lot of attention to those things then anyway. But with the mustang they were put together with quite a bit of bare metal on the internals.
It looks like both sides will need new floor pans, full length and a firewall patch on the drivers side at least.
Luckily they’re not very expensive, they’re just stamped sheet metal and $100 should get all the pieces. It would in theory be possible to go scavage some sheet metal from an ‘you pull it’ place I’m sure for someone with mad auto body skills and do it for free but that person isn’t me.
Personally I’d like to replace the entire floor pan including the tranny hump but that’s like $500 and if you don’t know what you’re doing (*raises hand*) then you run a very real risk of throwing the body out of true. Not to mention you have to take the engine and tranny out or you risk folding the car in half since the floor pans provide a lot of the strength of the car. The wonders of unibody construction.
On the plus side it doesn’t look like the cowls are rusted through yet. But as the most likely source of issues it’ll need to ripped open and repaired.
Also the floor support and frame bits through the holes looks in good condition. Floor pans I’m willing to tackle. Replacing major structural pieces would worry me.
Ah well my plan is to have it ready for Ryan to be the coolest kid in school driving up in a muscle car that’s as old as his father and having the 289 hi-po reverberating the windows. That gives me 8 years more. 
FYI the image isn’t my specific car although it’s what mine looks like, down to the lack of insignia and emblems. I just don’t have a image of mine handy and it’s up on jack stands and the doors are off of it waiting new window regulators. Sadly the previous owner had it painted black. The original color was Ivy Gold.
