No problemo!
Number 2 in the 1st picture is what the rear seat backrest hinge bolts to, in fact I think number 15 is the rear seat hinge pin (I think the lower seat belt mounting bolts onto it too).
You get numbers 2 & 3 included with number1 in the first picture, however, they arent cheap:
Part no: 7656913 (DS) Part no: 7656914 (SN) - FRAMING £270 GBP inc taxes
Thats each side...
However, all panels in all 3 pictures are welded together on the car, apart from number 2 in the 3rd picture, the outer rear wings, which I think are bolted on on Tempra`s & Tipo`s.
How bad is the rust? can it not be patched? I`ve never seen one rust there!
Just so you know, #3 in the last picture is known as the outer sill in the UK!