When I put new A body springs in the rear of my car to replace the stock ones it actually lowered the rear 1". My car came with the F41 suspension so I don't know if those had a higher rate.
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0CD4QFjADahUKEwjx5KOQ3IPGAhWCJogKHThqAEY&url=http://www.maliburacing.com/coilspring.htm&ei=nHB3VfGmAoLNoAS41IGwBA&usg=AFQjCNFbKKcEAs95yRGfve_JPEFjBZoZ5A&sig2=khyHhWdlgo4nLTS2MoYbXA
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0CD4QFjADahUKEwjx5KOQ3IPGAhWCJogKHThqAEY&url=http://www.maliburacing.com/coilspring.htm&ei=nHB3VfGmAoLNoAS41IGwBA&usg=AFQjCNFbKKcEAs95yRGfve_JPEFjBZoZ5A&sig2=khyHhWdlgo4nLTS2MoYbXA