quarter panels
When I did mine on the cuda a long time ago, I bought some 1/4 panel skins and only used the back portion behind the wheel. We also had to replace the inner vertical panel so the extra material from the full length panel skins came in handy.
Later when I did the dart sport , I only needed a small strip of material to replace the bottom 3-4" of one 1/4 panel. Again I utilized the left over 1/4 panel skins from the barracuda to supply this.
Not sure what gage the material was, but prefabbed rust repair panels are the way to go.
Bob