TR2/3/3A Whats up with these "a" arms

[Got_All_4]

Didn't remember this from almost 40 years ago when I had it apart the first time but there is a difference in the upper control arm design. One set has an open section and the other is completely closed. Can't find my manual to see if one set goes on a certain side or are they mixed in a certain order?

 

[TR3driver]

The fully boxed arms appear to have been a factory modification, listed in an amendment to the TR3 SPC (but with no change point given) and in the TR4 SPC. AFAIK they are fully interchangeable with the earlier, more open arms.

But each side does get two different arms, one of which is very slightly longer than the other, so they can overlap at the ball joint.