I need schooling on 67 dart tie rod ends

What is so different about the tie rod ends on a 67 Dart? They are all more expensive than the 68 and up ends. 67 has the same lower ball joint as 68 and up but a more expensive outer tie rod end. Does the tie rod end have a different thread on the other end? What about the inners also? I know the idler is an oddball, one year only.