Best ifs kit? rms, hdk, gt suspension, or magnum force?

thread jack: speaking of aftermarket front ends, does anyone know what coil over spring rates would be best for a street driven big block? mine rides like a 10,000 pound dumptruck, unloaded!
i have hdk kit in mine bb dart i have have tried 500lb 450 and 400lb the 400 gave me the best ride and performance with 10'' coil over shock 440 with iron heads