I tried to understand too.
My broadcast sheet says wheel cover "35".
In the 70/71 Mopar parts catalog, my OEM wheel covers are these ones :
As you can see, the part # ends with "35".
A coincidence? Maybe not.
If my reasoning is correct, your original wheel covers were these ones :
The part # ends with "50".
I don't know if I am right, but it's a possibility :)