found the info:
My notes indicate the B-body Hemi torsion bars were left #781 & right #780 bars with diameter of .92 inches.
The base Roadrunner w/ 383 used HD bars left #779 & right #778 bars w/ diameter of .90 inches
In my parts book, the 780 & 781 bars are listed under Heavy Duty section and are specified for all 440, 426 applications and also under "extreme Duty" applications.
The 778 & 779 bars are listed also under Heavy Duty for all applications except 440 and 426 engines.
Hope this helps.
Mike Mancini
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Plus 383 B and E cars automatically came with the 440/Hemi suspension (Xtra heavy duty) if they were equipped with an axel package like A31, w/3.91 gear or A36, w/3.55 gear ratio.