The idea with the small torsion bars is that they have to be cranked into a higher pre-load condition to support the big block weight and keep it up off the bump stops. When you launch the car, this pre-load helps pitch rotate the car backwards to provide a greater load on the rear tires and improve traction. Combined with a super stock leaf spring that lift under acceleration, and a properly set up mopar will appear to literally "jump" off the starting line.
Now, how important is that to drag racing? Depends on how tight your class is. If you're bracket racing, IMO, not very. If you are class racing, very important. My personal experience with that was demonstrated in two seperate cars, one set up as a canyon carver with higher rate t-bars and huge sway bars, the other with lightweight t-bars and no sway bars. The same engine/trans/gears/tires were used on both. The net result in e.t difference..1 second. The dedicated drag race ran 12.2, the canyon carver ran 13.2, both at 112 mph. Since the drag car never drove on teh street, I can't comment exactly on how its street manners were, but just driving the pits return road, etc, it had a lot of body roll, the rear rode rough and the front had potential to quickly bottom out. The other car, felt smooth and solid and by comparison, would feel confidence inspiring on the street where it could corner like a BMW.
