My old street car (iron headed 440 Duster) being a street, strip car, I ran the .870 bars. This gave me good street manners and yet, when I pulled up hard on the front end....with my hands....the front would rise over seven inches!! Most cars will never do that.
The things I do not like about old, used torsion bars (junk yard 6 cylinder bars) is metal has a memory. It has a natural state that it wants to stay in. When you have used bars the memory or the spring rate start to go away. A new "happy" bar, when installed and tighten up wants to raise the front end up but the weight of the car keeps it down. When you launch the car the momentum and the torsion bars try to pick front end up and put more weight over the rear. When you have week bars....the bars don't want to go up....there is no "spring" left in them so you get no help at all.
I will say this, every car is different and acts different. Sometimes older bars do work in a car but I have to ask my self why??