Welcome to the forum.
Panels might be available but most of what you need in that area is pretty straight forward and easy to make. I patched those areas of my LJ recently. A lot of the repair area will be covered by the flares and in my case the sill covers.
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The ends of your torque boxes (the rectangular "holes" in your pics) look pretty crusty. They are available and are a pain in the butt to replace in whole or in part. Follow them from what you show in your pics to the front wheel well area and prod them with a hammer, screwdriver or what ever to assess any damage. In my case one side was good but I had to do the other side. Torque boxes are welded to the floors and are integral to the strength of the tub.
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