Here's another technique you can try. Clamp a locking (vise grip) plier around the torsion bar about an inch from the spring plate (use leather or some other protective material around the bar). Use a couple of pry bars or large screwdrivers between the vise grips and the spring plate to evenly separate the two. Check the splines for burrs. Don't forget to lube the splines with some waterproof, synthetic grease so it'll separate easier the next time.
Hope this helps.
Sherwood Lee
http://members.rennlist.org/911pcars
www.seinesystems.com