I'm (still) working on the driver's side floor. I've got most of it out (https://www.youtube.com/watch?v=3MS07vuiuUk) except for the extreme rear (under the heelboard) and the extreme front (at the bottom of the A-post.)
Tried as I might, I couldn't get that damn piece out from under the heelboard. It's all of 1 by 4 inches (2.5 x 10 cm) and it's so mangled (from rust) and rusty (from rust) that I can't even see where the welds are. It's possible/probable that it's original but it's tough to tell.
In the front, at the bottom of the a-post, it's also difficult to tell what's going on. The PO installed a patch in the a-post, which I thought was OK, but tonight when I was wire-wheeling it, the wheel started eating away large gobs of the patch. Then I discovered that part of the patch wasn't even welded in (under the dash); it was only held in by seam sealer. Argh.
I also wire-wheeled around the radius arm mount (interior) to find the spot welds, which I did. That might be next, but I don't know.
Happily, I received an order from Rimmer Bros today including a new driver's side outer sill (which I was originally going to salvage, but I've discovered too much wrong with it, so it's going in the bin). I also got new front quarter panels for both sides, and a new rear quarter panel for the driver's side.
I should've bought a new inner a-post for the driver's side, but I didn't know it was bad... ugh. Shipping's a beast from the UK to the US!