Here's the right side of my Kelsey-Hayes disc brake '68 Barracuda. The wheel is turned all the way to the right so I could take the picture without moving the car and jacking it. Because of this, the sway bar tab is furthest away from the bolt. But you can clearly see the bolt goes from the back in, and is rounded on the edges. It looks to be very similar to your drum brake bolt head. I'm pretty sure the knuckle is tapped so there's no nut to interfere with the rotor.
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