1972 A Body (Demon) Spare Tire Hardware/Install
My spare tire is a 205/70/14 on a 5,5 wheel - too big (or too high) - You can see....
Original was a 185/70/14 on a 4,5 wheel in the trunk - this combination makes a flat floor.
It doesn't mind for me, but have a round cardboard - not like Yours.
For the black metal cup, I found another theory on a french forum : installed in the spare wheel hole (and under the jack hook), the metal cup helps the stud to be centered.
This sounds nice - and I tried it, but it doesn't work - because of the form of the holder - the fixing metal part/slot in the trunk.
But it fits exactly on/in the base of the jack.