Control Arms

[xnamerxx]

Can someone explain the differences between the NCP91-NCP131 Control arms?
I see different part numbers between the Yaris/XD and and the Prius C and 12 have a different part number but as far as I can tell there interchangeable but the track widths are vastly different between the cars so I'm confused, are the control arms the same or are they different.

The Prius C and 12 have a different crossmember and control arms but their track widths are pretty different so I'm pretty confused on what is actually interchangeable or not.

[CTScott]

Looking at the service manual, the NCP131 and NCP91 controls arms look identical.

[xnamerxx]

Thats whats getting me, the arms have different part numbers and the cars have different track widths, not totally sure what to believe. All the aftermarket arms are identical but the factory ones seem not to be.