The garnish moulding that is sitting in the front seat in one picture is not for a 3W.
Remember, the rockers and bottoms of the quarters rust because dust and dirt settles in there and then gets wet and retains the moisture in those areas where there is little or no paint protection, mostly bare steel. If the outer sheetmetal is rusted like that, the inner is going to be rusted as well. Rule of thumb for rust, there's always more there than you can see before you start cutting the rust out. The subrails will not survive unscathed when you have rust showing on the outside. They may not be as bad as they are heavier gauge than the outer sheetmetal, but they will have damage as well. They may be pitted or they may be swiss cheese. If they're swiss cheese then the extent of the corrosion damage can include the frame. Obviously, it can be repaired, but how far do you have to go to reach metal that you can weld the patch panels to? You really don't know how big the job will be until you get into it.