There are patch panels available for everything you need to do.
Floor panels from the front of the seat riser up to the toe board are available right and left side. You may not need the complete panels, but there will be the material you need there.
Inner, outer, and the infamous inner-to-outer cowl panels are also available, either short height or full height. You'll be swearing at the inner-to-outer cowl panel as you try to fit it in place. Just cut it where needed and weld it back together.
Your cab seems to be solid enough that you may not need a rotisserie. Some guys have laid the cab on it's back on appropriate padding to work on the floor. Be sure that you put temporary bracing in place before cutting out too much rusty metal so the cab doesn't get distorted. There are checking dimensions in the Factory Assembly Manual that can help you keep it correct.
You'll know more once you get it cleaned up.
Be sure to ask if you have more questions. I've been thru that effort (and more) and pics are in my signature link.
