After I got all I could with the sanding wheel, I changed over to a metal grinding wheel. When using this, be super careful because these can do a lot of damage. I worked really slowly so that I could get a nice finish on the metal. It was really good for taking the thick rust off and getting into those pits.
After 99.9% of the rust was removed, I sanded by hand (with 120 grit 3M Sandblaster sandpaper) to get a nice smooth metal surface.
If I wanted, I could have used Bondo to even out some of the dents, and fill the space where the paint is gone