I have a variation on Daves project.
I have seen the clips used on the flat surface between where the lug holes are located. A little different than Dave's side of the rim placement. you may wish to use 3,4 or 6 clips per rim. Then a short piece of tubing, be it copper, stainless or steel about 1/4 - 3/8'' diameter was placed so the fixing clip was placed on top of the short tube. You could then use a 10 or 12x24 machine screw to hold the clip in situ. There is room on the back side of the non stock rim for a nut. The tube may even be as long as 3/4 - 7/8'' (you will have to play w/ that distance to figure out your hubcap to clip and rim retainer tension. The distance or placement of the drilled hole is also determined by you playing around w/ placements. I suggest you buy a couple extra spring clips, they are adjustable to a point and brake suddenly.
this should work on 1/2, 3/4 and possibly 1 ton rigs.
I believe the ''second ring' is in the photo shot and not available, or as red58 says home made. It may also be the rim was painted silver and the cap then was a topper.
have fun

Jim & Caroline
The highway is for gamblers, better use your good sense."
Gooday-that's my 1¢ answer due to the lousy economy ~ cause I ain't got - no . mo . doe
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