Well, when I advised going with "a bunch of spring rate", my comments were made on the assumption that the car being prepped was going to be pretty much a track-only car. If the car is only going to see autocross and occasional track usage, there's no point in stiffening the car up so much that it loses it's comfort for the street. Our cars were built as big, comfortable cruisers that do everything fairly well, not really excelling in any given area ... just a nice, fairly quick, all-around capable performer. If you're going to end with something that rides like crap, just to get it handling a bit better for competition, you might as well start with a Mustang.
So my suggestions for a daily driver / sometimes weekend-warrior car would be a set of Suspension Techniques springs, because they are linear rather than variable rate, but the Eibachs would probably work almost as well in a slalom ... if you're a beginner, the difference would hardly be noticeable, if at all ... and the Eibachs will ride nicer on the street. A set of Koni Sport or Bilstein shocks ... the Konis may be advantageous to have because of their adjustability, you could experiment with the settings to change the front-to-rear balance of the car for an event. Front stab. bar I would leave alone, and on the rear I would go for the Addco 1-1/8" piece ... increasing your rear roll stiffness compared to the front, which should reduce understeer. Basically, the stiffest end of the car will lose grip first, so if the car is plowing on the front in
steady-state cornering (understeer), either the front roll stiffness has to be reduced, or the rear increased. This is where people will get confused, they goose the throttle around a low speed corner, the back steps out, leading them to conclude
"my car oversteers". WRONG ... take it through a sweeping medium to high speed corner, entering at the highest speed possible, then see what happens ... a stock SC will understeer slightly, not as bad as a stock Mustang of the same vintage though.
Your intention to stay on the stock wheels is going to handicap you somewhat ... a 7" wheel really isn't big enough for a 2-ton car in any type of handling event. You can put 245-50-16 or even 255-50-16 tires on the stock rims, but an autocross situation is where you would experience the excessive movement of the tire sidewalls, because the rim is not wide enough to stabilize them. For autocross, the stock rotor size should be OK, because you're just doing short runs, and the bigger calipers and pads will do a better job of clamping on them. However, on a racetrack, I'm sure that you will quickly experience fading and rotor warpage with that size of brakes ... again, just not adequate for pushing on a 2-ton car. If your budget allows, consider finding some 93 - up front spindles, then going with a set of the Mark 8 11.6" rotors on them. Unfortunately the PBR calipers cannot be used with the Mark 8 brakes, you're limited to the Mark calipers as well, which are bigger single piston units than the SC calipers. They also will clear stock 16" wheels no problem. I did several lapping days with that brake set-up on my car, using KVR pads. At one event at Shannonville, which has some tight corners and hard braking areas, while running on the Hoosier soft-compound road-race radials, I was getting the front rotors glowing
BRIGHT ORANGE after about 10 laps of really jumping on the brakes at the end of the 2000-ft straight (approx. 110 mph down to 65 - 70) ... and no rotor warpage.
Overall, I would say that the SC can be a fun car for events like this, but as you have already figured out, don't expect many trophies. Especially in an autocross event, the car is too heavy, wide, and long to get the job done quickly ... all the things that make it stable and comfortable at highway speeds work against you while trying to make tight corners and quick transitions.
Holy crap, I'm long winded today !!
cheers
Ed N.