BEWARE OF ESPO SPRINGS

-3 would put the rim above the wheel opening on a dart.

Stock level caltrac springs on a 70. With no weight (fuel/Battery) in the back end IIRC. With weight in the trunk, wheelwell lip is about even with a 15" rim lip.
ExXdlMS.jpg

Just a pic of what I have compared to yours...

The cuda is going to look exaggerated because the well arch is round, not squared off. The bad thing is if you had it sitting about the same level and it was high already, then you didn't get any additional height with the new spring. Might have needed +4. These cars are ALL over the place with measurements too.