There are only four way to suspend a car; coil, leaf, torsion and air. All react to road handling in similar manners. What differentiates a good handling car from others is the balance of those springs rates and geometry of the system.
In stock form, classic Mopars have reasonably good geometry that was way ahead of its time for its era. They do have some bump steer issues and a definite lack of caster, but there are parts out there to address that. What high end systems like AlterK and XVL2 do is seek to optimize the geometry while minimize the interference, weight, and bump steer that comes with the stock system while allowing faster and easier changes and increased adjustability in components and rates.
Firm Feel and Hotchkis have similarly addressed balance and rates in manners to retain very stock appearing systems. They also offer components that improve optimization while minimizing bad traits. However, because they are stock based, they are not as quickly changed out as the coil over types of systems, but they still retain a fair amount of adjustability.
FF, Hotchkis, and XV1 all produce good kits. They will make a car capable of outperforming 90% of the drivers out there and look stock doing it. They can accomplish this with a reasonable budget because they retain some key factory pieces and only update what is necessary. By contrast, AlterK, HemiDenny, XV2 and other conversion systems produce similar results with much less weight and a much higher price tag because they replace nearly every piece of the system within the car. They also look new and will get you a lot of compliments when others look under the car at them. Because they are made using later model parts, replacement items are reasonably easy and reasonably priced to get.
So do you want to be the guy who looks like he spent a bundle on his car and can hopefully back up the look with capability, or do you want to be the sleeper who smokes exotics while looking original?
