Safe disc Thickness? Odd anti-rattle/ retainer set up

I'm working on a 70 Dart with K/H discs. I can't read the minimum Thickness number cast in the disc. Does someone know what the number is?

I got rebuilt calipers and pads from Rock Auto, but they didn't come with the clips that retain the pads and keep them from rattling around. I looked through my disc brake parts and came up with the ones pictured below. I have never seen a set like this before. They say K/H right on them, just wondering if anybody has had experience with these.

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