Info on dust caps for Wide Five hubs/drums

[Ziggster]

I recently purchased some wide five hubs / drums (front and rear) and I’m now looking for centre (dust) caps. I found a bunch of the threaded variety from various sources, but wanted to know if these look like the original
Ford versions. Also, regarding the front hubs/drums, one is threaded for the cap and the other is not. Could someone please explain why one is threaded and the other isn’t, and where I can find a non-threaded version? I did find these NOS threaded ones on eBay, but seller says they are 3” in diameter. What would they have been used on?
I should mention that is the rear wheel bolted to the front hub/drum just for a colour comparison pic I took.