[bobcowan]

The chassis on the two cars is exactly the same. Anything that fits the Cobra will fit the Sebring.

The first step is to determine what you already have. IIRC, they use a Mustang II front end, and stock Ford 8.8 rear, with springs and shocks at all four corners. Lots of room for improvement there. You need to know what spring rates are already there.

The best improvment will probably come from replacing the shocks and springs with coil overs. It's not the cheapest option, but probably the best. Unless you're racing, don't bother getting double adjustables. Lots of money there, and not much return. Koni and QA-1 both make excellent products.

Springs are a place where you really get what you pay for. A $75 spring feels a lot differant than a $25 spring. I only use Eibachs.

In the front, it should be a "simple" matter of removing the old parts and installing the new ones; depending which lower arm is used. With coil overs the entire weight of the car is now on the shock mounts. Make sure they're strong enough for the job.

Same in the rear. As I recall, the shock is mounted vertically to the rear of the solid axle in single shear. That's fine for a shock absorber. But a coil over will need a stronger double shear mount.

What you're looking for is Suspension Frequency. A lot of measurements and calculations to help you calculate the "perfect" spring rates for your application. But, in general, the rear will be about 350-400#, and the front about 650#