If you think a 67 is ignored you should try finding stuff for the 64.
I'm doing budget math in my head trying to figure out what I need to do to get bilsteins and the 1.030" Torsion bars to go with my super stock leaf springs...
Super stock springs are not handling springs. Your car will handle corners much better with HD rear leaf springs. "64" suspension is the same as any "A" body, pick one and go with it. I used to tell parts guys I was working on a 71 340 Duster.