what QA1 spring to use in my 55 Belair

[smith & sons]

Currently have QA1 coilovers with conical variable rate springs.For a 3840 lb car it handles really well with a 7/8 in sway bar. They now have a 450 lb non variable rate spring.Would this be a better choice with a 1 1/8 sway bar?Looking for a little better ride with the same cornering ability.(QA1 states a 550lb spring would give the same cornering I have now )Front end weight is 1980 lb.