Here's a few forgotten about, and not too clear shots of when I pulled the 12 bolt out of my 67. I believe the line end is male into a female T junction at the diff. I think the line passes through the bracket, into the T and is clipped into place on the backside. The line end at the frame is female, clipped into place, with the brake line flare fitting into that. The frame end was a bear to get the flared end and tube nut out of the line. It was totally frozen, and attempting to remove it destroyed the hard line. There is about zero room to work up there.
I grabbed a screenshot of the 67 ends off Rock Auto,
I've got a 12 bolt diff from a 1968 Parisienne that I can take a look at. I'm pretty sure the brass junction block is still there as well as the bracket that holds it. Getting to the diff is the awkward part.
I just pulled it off and have it ready to go. I'll try to get it out tomorrow. If it turns out to be what you need we'll work out a donation to this site for it if you are ok with that.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars