What they found was the result of a LOT of abuse - lots of dump the clutch street racing or many full bore launches at the strip. The damage comes from the body actually twisting under the stress of the launch. The steel has been split open and needs to be reinforced and mended (welding in a battle box will do that). The body needs to be checked for straightness on a frame repair fixture first, though.
I would have them inspect the car thoroughly looking for similar damage. Things like the suspension (particularly the rear suspension) can catch heck in these situations. Bent control arms, split/worn out bushings, broken tranny or engine mounts, and of course mechanical damage to the drivetrain (clutch and transmission would be suspect).
Box supports are pre-fabbed steel designed to be welded into place right where you have your damaged section. If the damage is as you describe, I agree with your mechanic.
Check the vendors on AFM first to see if you can find a deal - I would start with LRS and StangSuspension. Adding a pair of subframe connectors (which should also be welded in) would be cheap insurance against any future flexing in the body.
I would have them inspect the car thoroughly looking for similar damage. Things like the suspension (particularly the rear suspension) can catch heck in these situations. Bent control arms, split/worn out bushings, broken tranny or engine mounts, and of course mechanical damage to the drivetrain (clutch and transmission would be suspect).
Box supports are pre-fabbed steel designed to be welded into place right where you have your damaged section. If the damage is as you describe, I agree with your mechanic.
Check the vendors on AFM first to see if you can find a deal - I would start with LRS and StangSuspension. Adding a pair of subframe connectors (which should also be welded in) would be cheap insurance against any future flexing in the body.
