Kelsey-Hayes proportioning valve for A body

Application is for 68 Barracuda with Kelsey-Hayes front disc and 10 x 1 3/4" rear drum. No junk please. Looking for nice rebuildable unit. Would rather have Mopar unit than a re-pop. Think it resembles this one if not mistaken.

View attachment 1716055970
Not to sidetrack, but I have one exactly as in the picture. What is the piece at the top circled in red? Thanks.
Proportioning valve.JPG