Same problem with my 74 450sel steering wheel.
I repaired it by removing the wheel to take it inside, then used small very sharp x-acto razor knife to split the covering where it was loose, on the unseen side of the padding, and spread it apart only enough to gain access to the steel rod inside, where I applied lots of Crazy Glue, and wrapped the section with wax paper, then with some sort of strapping material, and let it set.
There were some few small ridges where the fingers rest while gripping the wheel, but fine sandpaper smoothed that off.
It's been over a year, and it is still solid.