Did you happen to check these out over on FBO?
https://www.forbbodiesonly.com/moparforum/threads/64-fury-wiper-rust-out.168334/ https://www.forbbodiesonly.com/moparforum/threads/cowl-rust-repair.163953/I tried those mentioned above and those listed in these articles to no avail last summer and body guy ultimately built a new one. I believe the most challenging part was right around the wiper arm and he may have reused that portion. As mentioned in these articles you will likely find a mess underneath if you havent opened it up yet.
Good luck.
