Torsion Bars

I've got a 71 Demon that was a slant 6 car . I am in the process of restoring it complete with sb stroker. K - frame was swapped out and replacement comes from a 73 Duster. When ordering my new torsion bars do I order for 71 Demon or 73 Duster ? Really finding FABO very helpful and informative, keep up the good work.

Thanks