I have not done the 2004 X3 yet, but I used Lesjofors springs for my 2003 325i.
I love the Lesjofors springs, they sit perfectly.
I posted a DIY REAR spring for E46 3-series below.
Same trick for E83 X3.
DIY: 2003 325i 95K REAR Shock/Mount/Spring installation
https://www.bimmerfest.com/forums/sh....php?t=1357037