Torsion bar question for 440 A body

Hi again folks!
Was thinking about what recommendations for torsion bar sizes you might have for a 440 Duster, with a 4 speed. Nothing too road race style just a fun weekend cruiser with an occasional burnout. I am planning on power steering, manual disc brakes and possibly air conditioning. Also I don't see any markings on the existing ones how can I determine what I already have...

Thanks again!