Thanks Deb! I'd forgotten that I actually have the Fergus Henderson book that those recipes are based on. (it's upstairs and we've sold and not rebuilt our staircase, long story)
So the beef shank was basically a cut of meat with some bone in it, it wasn't quite what I needed for marrow. What I had in Paris looked like this:

I was on a mission by this point though so we stopped by Kingsley's and they scrounged up a few bones they said would work. Only one was more than an inch tall though. We roasted them at 450 in a cast iron skillet. The three small ones just melted away all the marrow. The one little taller one kept maybe a tablespoon of marrow. The taste was right but the texture wasn't as light and melty as it was before. It was also still a little pink but I thought if I cooked it any longer it would melt away too. But at least my husband was able to get a taste and see what I'd come from from France raving about.
Kathy Packard at Misty Meadows Farm is going to try to get me some leg bones that will work. I'm still determined to have this amazing dish.
I don't imagine any restaurants in Louisville are doing marrow, but if you hear, please let me know!