M3 sub frame rear toe mount points are 23" apart, center to center of the holes.
CONFIRMED! Non M3 E9X rear sub frame has longer distance between mounting point to king pin / spindle for rear toe arms.
M3 sub frame has the mounting point visibly more outward position.
First one is Non-M3, the second one is M3 rear sub frame.
So it was a good thing I bought used M3 rear toe arms for $30 each
Let's hope I won't need M3 lower control arms, that would mean I will have to use M3 rear dampers as well!