Larry,
Momo discontinued their 15" wheels, and now all they make is 12", 13", and maybe a 14" or two. They must think everybody drives a Honda! It's very sad but the wheels they make nowadays look awful.They make nothing now for Jaguar after Ford threatened Momo, Motolita, Nardi, and everyone in the aftermarket accessories with legal action if they made Jaguar horn button emblems or any accessory with the Leaper or Growler, so you cannot get horn buttons with Jaguar emblems anymore, unless they are nos or used. I was lucky that I got my Momo Olympic from a business that was closing in 1992. They sent me a growler and leaper Momo horn emblems, which I am using in my two Jags.
Save your Momo, they are becoming rare. MossMotors has the hub kit for the MK-1, MK-II, S type, and 420. They also have a line of leather and wood steering wheels called "Tourist Trophy", very high quality and cheap! They have a thin version and a thick version which nobody makes. However, I don't think they would look good in the XJ-6, they're mostly for old classics.
Ex