jasperjacko:
I cannot say that they are the correct ones. They do fit correctly, though, on both the 5 on 5s and on the snowflakes. I actually bought them for the Imperial snowflakes, and then found out that they also fit the 5 on 5s. If they aren't the correct centers for the 5 on 5s, I will use them until I can find the correct ones (if they can even be found). They fit securely (the spring prongs do fit the grooves in the center holes perfectly, and the center hole ridge fits properly under the wheel center), look fine to my eye, and in the absence of any "real"/"factory original" 5 on 5 centers, they will do just fine for me.
I would really like to see what your center caps look like, and it would be a good reference for all on the board in terms of what to look for, and how to determine which is the correct cap when at swap meets. Maybe you could get the part number of the cap on your wheels, the part number of the caps that I have is in the picture above.
Kostas
P.S. I just looked at my snowflake wheels, and fit the same center on both the 5 on 5 I posted the picture of, and the snowflake wheel. Seemed to fit properly, and very securely, on both. Also measured the actual diameter of the center hole on both wheels. Both were 2 5/8" using a tape measure. There is also the same ridge to secure the spring prongs inside the center hole on both wheels. The 5 on 5 has a extended edge around the center hole on the outer surface, the snowflake doesn't, so the center cap on the 5 on 5 sits further out on the 5 on 5 than it does on the snowflake wheels.