Bill, I've got a set of 4 original gray Magnums from my 66 GT-350 back when I owned one (6S524). They've been sitting up in my rafters since the 80's. Back then I had them powder coated, but wasn't satisfied with the color, too light, too much gloss. Decided to run polished 7 x 15 Pantera wheels instead. I posted some pictures of them here way back when I use to frequent this site, but looks like all my postings are long gone.
You can paint chrome ones gray, but I think the seam on the gray rim was a bit more visible than on the "C" part number chrome version.
I'll drag them down and post pictures later. They need to be stripped and repainted.
Ken