Our exclusive Detroit Speed F/X-Body Speed Kits are designed to work as an integrated system on your vehicle. By utilizing our proven Detroit Speed components and carefully selecting components designed to complement each other, each speed kit is for your driving needs with the ease of a bolt-on package. Speed Kit 1 is designed to bring your classic GM muscle car into the 21st century with improvements in ride, handling, and camber/caster correction. Speed Kit 2 takes performance to the next level with coilover shocks and springs that provide ride height adjustment. Speed Kit 3 is the most advanced handling system you can buy for use with the stock subframe. It gives you the ultimate steering performance of today's modern performance cars. Spring Rate: 550lbs/in or 650lbs/in, Spring Free Length: 9.5in.