torque boxes

You want the ones with a poly bushing on one end, and a spherical bushing on the other, to prevent bind. Double poly bushings will wreek havock on your torque boxes, and from what i have read will present some crappy handling characteristics.
 
If you plan on racing the car, which I'm sure you are, you should ALWAYS (at least) weld the torque boxes. You really should reinforce them. Launching a car hard on slicks, or any sticky tire, do lots of chassis damage over time.

Joe