The studs on the arms I have both point down, both the one on/off the car and Proforged 103-10031. I think they're a generic B/E Body fitment and would technically fit the 73+ a-bodies if the steering sector was smaller.
You could not install the Proforged 103-10031 so the stud pointed up because the bend in the arm would make the end occupy the same location as the starter. I'm pretty sure its tapered as well so it can only go on one way. I guess to use this arm on the pre-73 A-bodies you'd need a 73+ centerlink. Interesting they wouldn't note that in the part description.