Lots of PB Blaster, some heat, some patience, lots of time in front of the sand blast cabinet and too much money. Thats what it took to restore my big bolt mirrors. I got real lucky and found the actual mirrors on the "big auction site" as Mike says and they were at least close to the mirrors that were on the truck when I bought it. I doubt they were original at that point. My frames has several layers of rusty crusty paint on them but they came out very clean. Obviously I went to the expense of chroming mine but painted would have looked great too. For me, I like these original brackets with the additional supports etc., that's why I went all out.
I think yours will clean up good too.
Good luck.
https://photos.app.goo.gl/uwqZF6DCC2GmiZS9A
