A-Arm Early vs. Late, Any differences for ball joint install? Options

[BeatNavy]

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).