The root of the confusion is the steering gear box. What/which steering gear box is used will determine the box coupling, pitman arm, idler arm, and center link required.
Yep, like he said. If you have a 72 and earlier steering bow it should have the smaller diameter sector shaft, and must use the corresponding pitman arm and therefore center link and idler arm. If you have a 73 and up (or earlier manual box out of a b c or e body) it should have a large sector shaft and will need the required 73 and up pieces. Also, as was said before, inner tie rod ends are the same, but will need to be rotated 180 degrees if you change the center link style.
