As far as I can tell, your wheels WILL take traditional snap-in hubcaps
Here are the basics:
A traditional snap-in hubcap has plastic tabs that recieve tension (pushing outwards) via a metal ring...
When you push the hubcap onto the wheel, the plastic tabs snap into place in this groove...
You will also notice that on snap-in hubcaps, there is an indent in the ring as well as in the hubcap to accomodate the Air filler nozzle thingy.
On older hubcaps, and most metal hubcaps (possibly the moon caps), they are still snap-in, and follow the basic idea but with a different method. All the little metal tabs snap into that groove, but they don't need a tension ring because they have enough tension on their own. This connection is much more stable than the plastic tabs with a metal ring, so if the moon hubcaps have this, they will probably NEVER fall of.
Older plastic hubcaps use the same method, with just a few metal tabs instead of metal tabs all the way around. Even these are better than the plastic tabs... I just about fell over when this hubcap finally popped off the wheel, I was pulling so hard!
And believe me, when it comes to hubcaps, I know what I'm talking about
Here's my "collection"...
I hope this helped