The A-pillar area
The first sign of damage was in the inner rocker panels. The entire panel to the frame girder had to be taken out.
Rocker panel area, floor panel, and interior
The rocker panel area is the second critical location. Several panels run together here. Rust prevention was almost nonexistent in the sixties. Therefore, you'll encounter many a surprise here. The exterior rocker is often intact, but behind it is only rust!
After the floor panels and rocker panels are welded in, the seat rails can be welded in too. There are two different rails for each seat. One has the upper piece and the bottom piece welded together. These have to be taken out from the car floor and then welded in again. The other rail comes in two parts. The bottom piece can be obtained as a reproduced part and is welded to the floor panel. Two M6 nuts have to be welded on top of this rail. The upper piece gets screwed into those. This way the width of the seat rails can be adjusted.
Here is a schematic for the structure of the rocker panels for the coupe and cabrio. On the cabrio only, this area is reinforced with extra panel. Many of these panels are available as new reproductions so they don't have to be laboriously made by hand. The following parts are available:
Inner rocker panel
Outer rocker panel
Slant mounted perforated plate
Innenschweller: Inner rocker panel
Aussenschweller: Outer rocker panel
Tuergummi: Door molding
Schwellerzierleiste: Rocker panel trim strip
Bodenblech: Floor panel
Rechteckprofil: Rectangular profile
zusaetzliches Versteifungsblech mit Sicken: Additional reinforcement panel with beading