6 cyl. Tourque Shaft ?

(guess torsion bar is the correct term here).
Is for a SS Nostalgia Racer.
My concern is to get a proper set, or is a "worn out" set ok or even an advantage like with front shock absorbers? I mean I guess there are some difference in a new and an old set of bars tension wise?
Or can all this be over looked? Get any set of 6 cyl bars and I should be good..
Nostalgia Racer here means SS Springs, long shock absorbers and adjustable pinion snubber on a 4-speed car. Tires 10,5X30" some…
Appreciate your thoughts around this.
Thank you.