What proportioning valve is this?

My 68 Barracuda came with the brake parts to do a front disc swap when I bought it. Everything was pulled from a 67 Formula S. I’m trying to figure out the proportioning valve stuff. Attached is a picture of what came with the 67 stuff. Is the prop valve the smaller boxy thing? What is the roundish cylindrical thing? Thanks. I WILL have more questions as I move forward on this. I also need to see if the calipers are rebuildable.

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