I did my 73 15 years ago. The only thing available were 1/2 quarters. Just cut the parts it needed. The area in front of the wheel us very close to the outer rocker. Mine had pine needles between the two panels. They had formed to a hard mass like OSB board. No way you could had removed them without cutting the panel. My panel showed very little rust from the outside. Glad I cut it. Still perfect today.
Doug