Working on Leighanne's Willy 1 again...I happen to take off the steering wheel and straight away notice this one uses the different design column, wich uses a nyloc nut on the end of the column, which is a threaded section rather than flat.
Both my cars have had the big torx bolt that goes down inside the column. The other thing I think is different is the length of the splines. Hers seem shorter.
I happen to have The Nana's steering wheel in my possession and tried putting it on to see if it makes a difference and due to the apparent(?) shorter splines, the Nana steering wheel does not sit well with it, leaving too much play and visually not going down the column far enough as well.