The problem with these rockers is the foam, the lack of proper coating, and the sunroof drains.
That sherman outer panel will work fine, BUT the real problem is behind it. The actual structural rocker sections were super expensive, and of course no longer around.
They rarely rust from the front. But to save your fender, just trim that insulation, and replace bottom spacer tabs with simple washers to allow water to drain out.
If you're seeing any kind of corrosion and rust on the outside, you can bet your rockers inside look like in the pictures below. Your best bet it to get a section of the rocker from a rust free donor car, cut and replace as needed.
This is one of the most complicated sheet metal areas on this car. Been there done that. Never want to do it again.
