It absolutely makes a difference...in Stock and Super Stock, you are not permitted to permanently attach a ballast/weight box to any part of a roll cage/bar. However, in most of the other classes you can. I would weld in a crossmember in the back and mount the box to it. Otherwise, contact your local Div. 2 NHRA Tech person and discuss it with them.You guys are missing my issue. Stock or super stock, makes no difference what class or where the box is located. I'm not talking about what works best but what is the legal, acceptable, way to secure the box in the trunk of a unibody car without getting into a major deal.
The only permanate weight I'm talking about is the weight of the weight box. You're allowed up to 100 lbs. of removable weight in the box.