Macobra,
Don sells a kit, I think Carrera. QA1 makes a nice adjustable rate shock one also. You can order different spring rates, so there should be no need to cut the springs.
http://www.speedwaymotors.com/p/182,...Over-Kits.html
I did have to make a 2" spacer since on the CR there is the welded bracket that extends the shock tower mount where the upper shock bolts on.