I wrote the site about the Momo adapter linked above..
“I see that this is notated to be for 1980+ W123 vehicles. However, i want to confirm that this will work with my 1985 W123. Will it? I have seen many other steering wheel adapters that only work for vehicles up to 1983, so won't work with 1985. Is there something different about this one that ensures it works for up through 1985? Thanks!”

They promptly wrote back!..

“I'm sorry I'm not able to confirm the fitment of this Momo Hub on your 85+ W123. We do not have the vehicle to test fit the hub. If you do find more information please so share with us so we can update the description.

Best”



Hmmm so where am I at? What’s my approach here? Start taking apart and measuring stuff?