I've done this on my 68 800 and boy is it tedious. As you've seen, the bezel is a crimped ring and a one time use; but we can cheat. Carefully pry the wedge shaped crimp on the ring wider from the back side with a small screw driver and Oring pick. Do it in several passes around the circle. Don't bend too much at a time. If the metal stretches to much, you'll knarly peaks and ridges when you go to re-crimp it again. When it is loose, you want it just loose enough to barely slip over the gauge pod flange. Then you're free to clean and paint. Work on a soft surface such as a terry cloth towel underneath to avoid scratching the rings. Be very careful about the gauge face finish and numerals. They're very delicate at this age. If you need to clean off spots, use Woolite (pink labeled) and Qtips.
For polishing and cleaning, the best stuff out there is White Diamond Metal Polish. Keep polishing until the cloth no longer turns black. Let it dry, and then buff. Whatever it's on won't corrode again for years. Your knobs are pretty far gone, but the polish will help a lot. NEVER use steel wool or other abrasives, you'll strip what remaining chrome there is and you'll have ugly base metal which is usually die cast zinc and corrodes easily. Painting as suggested is a option I've never used, but zinc is a funny stuff for paint to stick to and I wonder how long it lasts.
To re-crimp the rings you'll need precision pliers as a small pair of Knipex pliers. Cover the jaw serrations with 2 layers of electrical tape. Carefully squeeze the crimp back down a little at a time going full circle just like you did when opening it up. Use the outer edge of the bezel ring as a fulcrum point, don't just squash it front to back or you'll leave marks that you will see every day you drive the Scout.
