question about rear springs

My car is a 1965 Barracuda.

Sooner or later I'm going to add a set of anti-sway bars, good ones, to help a bit with handling. While researching the topic I found that the Formula-S package boasted stiffer rear springs than the standard version of the car.

This may seem like a basic question, but what's the point? I mean, exactly what benefit would it give to the handling of the car? I'm asking because my springs are sagging a bit and before I replace them I'd like to know if I should get the same stiffness as it was originally, or add stiffer springs to the vehicle. I'm also curious about how it was made to be stiffer. Just an extra leaf? Or perhaps it was the bend of the spring.

I'm not at all interested in going for a raked look. The much larger rear half of the car already creates this proportional look to my eyes. My Barracuda will only ever be a peppy street car, but there are lots of curvy roads around here that I fully enjoy driving on.
Author: admin