I had the same thing with the driver's side of the cuda above the window. I just had to buy plate steel from Lowes and bent up a u-shaped piece and started welding it in. The lower part by the windshield and the lower door opening was also badly rusted. I had to replace parts of it with the same flat steel. The door opening took 3 separate pieces to complete it. Don't you just love rust? Right now I'm replacing a big chunk that the lower passenger fender bolts to.
Good Luck with it,
