you can see the main rubber spring mounts in the center of the spring. There are also rubber pads on the end that should be present. The middle ones are trimmed down to alter the mounting height and preload of the spring (basically letting it un-arch itself for a softer preload). This results in the car dropping down. Further preload is increased by adding aluminum shims to the top of the spring bushing which pushes the center down even farther increasing the initial tension (raising car). Different models have different spacer depending on desired ride height and vehicle weight and spring type. Convertibles have 2 shims for the extra ground clearance, ZR-1's have 2 due to the weight of the LT5 (best I can figure). Other models have a single shim.
Not shown here, but the other side of the rubber bushings are completely removed- I was changing this spring for stock that I traded for.
Here you can see the shims removed and mounted on the bottom (just going along for the ride- nice of the last owner to have not thrown them away- they are normally on top of the bushing pack)
