torsion bars / drag racing

The /6 bars work like this . They travel further with less resistance. So the more they are wound the further they travel before reaching nuetral.

Hence more inches of upward travel with help from the spring pushing upward.

I had them in my car and it did help on the launch. but the downside was every dip in the road while driving normal (I mean slow )the header would bottom out on the road.

You need some big numbers to hold those bars in a jounce position for a quarter milewith a 3100 lb car.

They work with SS springs that is what they were commonly used with.

I think once you go to standard leafs, cal-tracs or coil overs in the rear you throw all the early science out the window.
I would go with the stiffer bars. Thats just me.