Same as above, but you can reset the torsion bar at the rear by extracting it and changing the axle position before re-insertion. Be sure to get the 2 sides even!
I Took 107mm off the rear height of my 2nd R9 (bit too much though

)a few years back like this.
I Never had the need to change the torsion bar for a different one and i used standard shocks too.
Regards, Dave S, 07939 989655