Is this a symptom of worn out torsion bars?

Just for your information, a Slant Six weighs the same as the 3.31" stroke LA motors and the 360 is only 25# more. From BigBlockDart.com:
331/354 Hemi with alum. intake and water pump ------504
392 Hemi with alum. intake and water pump ----------564
Slant 6 ---------------------------------------------525
273-340 --------------------------------------------525
360-------------------------------------------------550
361-400 --------------------------------------------620
413-440 --------------------------------------------670
426 Street Hemi ------------------------------------765