Given you donít have a sway bar, Watts Link, or Panhard Link, I guess Iím a little surprised it oversteers. But thatís a more comfortable way around the corner provided itís not acting like a drift car. My personal favorite is the adjustable Watts Link since moving CG (Center of Gravity) is a simple ten minute adjustment, a tight car that refuses to rotate can quickly be loosened up to rotate easily. And you donít really need to understand anything but the very basics.
The Fays unit has proven to work and to last. Some good quality, round, short, mufflers and side exhaust is an easy way and it does not have to be harsh. You can get the exhaust out the back, I ran mine that way for a couple of years, but it takes a muffler shop with a guy willing to get it done. And a big tip when he does.
Back in the early seventies the general idea was to spring it hard and dampen it hard, not a very compliant suspension. That thinking has evolved to spring it soft(er) and dampen it hard(ish). Or dampen it to the needs of the track. So softer springs will allow the suspension to work and follow the bumps and dips, dampen with adjustable shocks to the needs of the track, add the Watts, and youíll find you can fly. Or just do the softer spring that you want, a Watts Link, and youíll still enjoy a car thatís easily adjustable for the conditions.
Small changes in spring numbers is hard to feel, big changes may get you in territory you find too soft. If your current spring is too harsh, maybe itís the damper (or lack of) thatís the real issue? You know your setup far better than me, I guess Iím just voting for the Watts.
They do have a composite single leaf (sort of like on C5 and later Vetts), it knocks off some sixty or more pounds. Just a thought.