2005 CV LX Sport rear spring info

Looking to replace my air suspension rear springs on my 2005 Crown Vic LX Sport with a pair of performance rear coil springs. Looking at the Moog Cargo Coils as one option. I know there are others out there. Want to keep the same height, but want springs to be firm enough to compliment the rest of the suspension, but not ride like a dump truck either. Appreciate any suggestions or options you know of.
thanks,
JH
Fort Worth, TX