Doomedfailure:
The torque boxes are where the upper control arms connect to the frame. They can crack if subjected to a lot of hard launches (since the differential is twisting during acceleration).
You have a few choices: check the upper control arm bushings as they may be worn out, or, you can have the frame adjusted, or, you can install adjustable upper control arms. If the bushings are still in good condition and the torque boxes are not spread or cracked, I suggest adjustable upper control arms over tweaking the frame. The adjustable UCA's allow for easy future alignment of the rear and proper setting of the pinion angle if you lower the car.
A Haynes manual is only 20 bucks at AutoZone or Border or your local bookstore and well worth it, imho. It has tons of good info and photos and is an excellent reference for us weekend wrenchers.
Chris