Steel wheel, SBP

Hi All.

I have a 1970 Australian Valiant, it is based on the Dart.
The front hubs are Australian specific.
The diff it Australian as well.

Recently I got a 15" SBP wheel from the US to try out and I have a few questions when I compare the mounting of the 15" US wheel to the original Australian 14" wheel.

When you look at the two wheels and the mounting surfaces there is a difference.
Both wheels have two 'rings' one on the inside of the 5 stud holes and one on the outside. The difference is that if you put a straight edge over the inside of these 'rings' on the Aussie the wheel you can see that the two rings are level. But on the US wheel the outer ring is more inboard than the inner ring. (Red arrow in picture)

As the mounting surface on the front hub and the rear drum are flat it causes the US wheel to only make contact with the hub/drum on the outer 'ring' where the Aussie wheel makes contact on both the inner and outer 'rings'.

You can also see in the photos of the wheel mounted that inner hole of the US wheel seats on the front hub but when mounted on the rear the inner hole of the wheel does not make contact with the outside of the axle shaft.

Is it safe to have the wheel centring on only the wheel nuts on the back wheels? I am a bit nervous about this.

If I have not been clear please let me know and I'll provide more pictures or diagrams.

Thanks