spring&shock
If you want to lower the car, then you would pick a different spring/shock combo than if you wanted to keep the stock ride height.
If you want to drag race, one setup is better than another one for auto crossing.
If you have the money to spend you might want adjustable shocks (like QA1) and/or "adjustable" springs (like the Ground Control Kit w/Eibach Springs).
There are a lot of options to chose from.
Most people with "simple needs" and jsut wanting to lower the car get an Eibach Pro kit, and Bilstein HDs for a LS1.

