here's my understanding with a quarter mile bent on them;
stock soft bushing = allows squat, and results in quicker weight transfer - you want as much weight over the drive tries as possible.
"upgraded bushings" = read: for autocross/handling; slows weight transfer because it resists movement better than rubber.
Rear Sway bar = read: for autocross/handling; prevents weight transfer; I have understood that often quarter mile guys will effectively disable the rear sway bar to permit movement
Rubber spacers under the springs = this is a "for looks" modification; this also shifts weight towards the front of the vehicle, and effectively raises ones "cool" quotient, because it makes it easier to do a burnout.
There's a reason why older race cars would have their noses in the air...
http://www.speedhunters.com/2013/05/...nce-and-style/
This might not be a perfect example, but hopefully you know what I'm getting at.