When you say the ridged section in this photo

I think what you're looking at is the support for the seat rail. The photo below is from my swb, but I think they're all basically the same. You'll see where the base of mine had rotted out and I had to fab a new piece before rebuilding the floor. Remember the car is upside down on the spinner in the photos. Not sure why you can see it so clearly though - has the floorpan dropped down in the photo?

You can just see it in this shot of the lwb as well

As long as the base edge where it is spot-welded to the floorpan is solid then you are ok - you just need the floor-edge piece. You can get that as a repair panel if you haven't already got some.
Mick












