I'm doing some rust treatment / prevention on my underbody, and I've removed the control arm assembly from my early car ('72 MY, Nov 71 build). I've got a control arm assembly from my '75 project car cleaned and powder-coated with new bushings (almost) installed. My plan is to install that assembly on my early car.

What issues will I run into, if any? The PET shows the same P/N for all years. If I look at a picture of the part where the ball joint inserts, it does look a little different where the tab is or should be (see pic). I tried to put this A-Arm up into the ball joint on my car for test fitting, and it was fighting me, so I was wondering if there are differences. I know ball joints are different early/late, but I'm assuming that's primarily because of the pin or bolt used to secure them.

Also, the tab appears to be broken on the early assembly. Is that tab critical, and I assume people just weld something back on?

Pic below early is top (and dirty). Interesting, the sway bar mount seems to have come attached the early A-Arm but the late one has a bolt on (the hole).

Click to view attachment

Sway bar mounts came on early cars even without swaybars. They were an option on later cars. I don’t think the early vs late A arm makes any difference in actual use. You are correct, ball joints style correspond to the proper strut style.

The struts are different, how they attach to the ball joint.
A arms all the same,

My '73 has no swaybar yet I have the tabs on the a-arms.

Same with all my 71’s. But I had one 75 without mounts and one with mounts and bar.

Thanks, fellas.

How about those tabs that I guess hold the ball joint in place so it doesn't spin? Critical?

No functional difference. One is a spot welded tab the other is stamped out ot the A arm metal. Looks like a cost reduction by eliminating a part and extra operation.