The choice of 460 lb/in. fronts and a 330 lb/in. rear spring would be about right for a street high-performance small block. That is not road raced or autocrossed.
Stabilizer bar choices sould be 1-1/8 front bar and either a 1/2-in or 9/16 rear bar.
As for bushings, in the front, I prefer the Global West Del-A-Lum. It's the best street high-performance bushing there is. They tend to be a bit pricey, however, so graphite-impregnated polyurethane is the next-best choice.
At the rear, I like Vette Brakes and Products' "Smart Strut" kit along with polyurethane trailing arm bushings. Again, make sure any poly bushings are the graphite-impregnated type. They are less liable to squeak and groan in cold or damp weather than are the non-graphite units.
Keep in mind that with C3s, any bushing with compliance lower than the stock rubber stuff, will transmit more road noise and harshness into the cockpit. Those cars are already harsh and noisy so if NVH is something you already don't like, I'd stick with OE rubber bushings.
As for shocks, I've tried a number of different brands in my years as a C3 owner and I think the best choices are Bilstein or Tokico. If you go with the Bilsteins, you have a choice of two different valving choices. If you are mainly an easy driver but make an occasional sporting drive with on a club run, use the "HD" Bilsteins. If you run the car hard a lot, use the "Sport" Bilsteins.
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