RK Sport Aluminum Drive Shaft
Description: A very light single piece drive shaft.  It is 3" in diameter.
Price: RK Sport, Inc. $309.95
Install: Chock the front wheels. Jack the car up by the pumpkin and have at it.
Pro's: Don't have to worry about when the 2 piece will snap. It's lighter than the stock 2 piece by far!
Con's: It's over priced.
Verdict: I feel a lot safer with this drive shaft in the car. $309.95

3.73 Gear + Zexel Torsen LSD
Description: The Ring & Pinion and the Differential. Transfers the power from the drive shaft to the back axle.
Price: T. Byrne Motorsports + SLP Performance Parts Inc. $289.99 + $99.95
Install: Not something the average person should attempt. Measurements need to be precise or nasty gear whine may occur and damage to the ring/pinion will result.
Pro's: Gets out of the hole a lot quicker.  Leaves 2 trails instead of one.
Con's: Very Pricey.
Verdict: Knocked .4 off my 1/4 ET. $389.94