F2007 Steering knuckle with 8.2 mm axel. This seems to best fit, at least for my construction. However, this is also slightly tight. Also this seems to be slightly too high which generates some friction to the steering. But the 0.5mm - 1mm backlash with the original is gone :-)
I think Shapeways objects tend to have very slightly too much material on the surface, ie the holes are slightly (~0.2 mm) too small and the outer dimensions about the same too large. I had knuckles with 7.8 - 8.1 mm hole, but removed them (they don't fit, at least on my copy). If you want to test them, please send a note.