Are you sure those are slugs filling holes that used to be there? Below is a photo of a Minilite wheel used on one
of the Penske cars in '69. The photo was taken at Mid-Ohio in 1969. You can see the circular casting lines of a
4-bolt pattern besides the 5-bolt holes that have actually been drilled out. I wonder if the circular lines you see
in your photo are simply casting lines which are part of the mold for the wheel. Because the Minilites are 8-spoke
wheels, a 4-bolt pattern lends itself more readily to the design but, of course, the American pony cars were all
5-bolt pattern (in stock configuration). I'm not sure how AMC was able to get away with running a 4-bolt hub
and wheel as they were not stock that way. Since they were able to do it, I don't see why the others couldn't.
Since you are an AMC enthusiast, can you shed some light on that?Photo by Ron Lathrop