Thanks Vibes. The rust is so severe that I doubt there's enough chrome left for them to look even remotely acceptable. I've found a clean(ish) 16" hoop in my "stuff" pile and another that's at least better than what's on the drum right now. On moderately rusted hoops I find aluminium foil and water or white vinegar works well, too.
The parts that I'm missing are the square eye bolt that goes inside the mount and one on the BD mount is also missing, plus one wing nut.