Of course you can cut them.
However the design of the spring doesn't always lend itself to cutting.
The spring on the left you can't really cut but the spring on the right you can.
Doesn't seem to be many people running their stock Z's at the 1/4 mile on their forums either. They only talk about the AMS car running 10.7 @ 128 with god knows how much money into it.
C&D got a 12.7 seconds at 115 mph