Reviving an old thread.
I have a 20017 300 RE that my sachs rear shock blew the piston band and wore the hard anodizing off the shock body. Since I have never realy been happy with that shock. I decided to experiment.
2013 KX450 shock . 10mm shorter . Needs minor machining of lower clevis only. I re-valved it with a gold valve set up.
This worked good if I moved the forks up 10 mm and set sag @ 100mm. But the bike never really felt right. And I did not like the ride height.
Next up I got a Showa off a 2007 CRF 450. 1mm shorter. Lower clevis requires more material removed than the KX and the upper shock mount needs 1mm removed to clear frame. The remote reservoir also sits higher so a bit of material needs to be removed from the sub-frame and a little plastic removed from side panel to allow shock adjustment. I also re-valved with gold valve . I have now put 15-20 hrs on this shock set up and love it.