I am running a Hotchkis Sport Suspension 1903R  F-body rear spring that has worked out pretty well.  The top 3-4 coils are stacked so if you want to trim a bit more off it works great.  Leaves more room for exhaust going over the rear as well. I wanted the rear of my car low as possible with the 275/60's I am running so ended up taking off an additional coil AND didn't run the isolator at the top of the spring to the frame.  Put a high quality rubber hose right over the top coil of the spring.