Weight comparison between a Hemi Dart and a Hemi Barracuda.

Well let us narrow this down even more to the rear torque box only, that you found on the Formula S BB 4-speed cars, and most, if not all of the SB manual trans cars.
Have yet not seen any picture of any of the SS hemiĀ“s having the front reinforcement box, that the convertibles had.

I must correct myself here...in that all the BB cars had the rear leaf spring hanger mount boxed, not just the 4-speed cars.