I know you said you don't want aftermarket, but rather than a Grant, you could get a Nardi. I got a wood-rim Nardi for my '68 Dart years back, and they have a Chrysler adapter. It's nicely made and although aftermarket, it looks like you intended to do it, no that you had do do it.
Pricey, though.
Edited to add: Just read the whole original post, sorry. I see you want to keep your horn ring.
But back to the Nardi: I've kept it all these years because it was too nice to sell with the Dart. Since I have the adapter for Chrysler, I'd put it on my Imperial, if it would work with the telescoping feature. But it won't, so it stays wrapped up in towels and a pillowcase, waiting for the right project car to come along...