Its hard to say as the butt dyno and how its applied to handling can be very subjective calls. Its even possible that cars can be mechanically capable of each other but one simply feels better because of geometry, alignment, seating, or any of a myriad of differences.

When I played in the GM world, street performance spring rates were around 400#, which is around 200# in the torsion bar world. Classic Mopars can easily get to that point. Then it becomes controlling the motion (shocks) and improving the geometry where ever possible. Mopars overall have better geometry than many of their contemporaries, but the shared cast/camber of the upper arm eccentrics become limits pretty quickly when chasing down really good alignment numbers.

Another problem with larger torsion bars is that the chassis may not be able to handle the larger bars. Essentially the unibody becomes a spring. If subframe connectors, torque boxes, etc have been added, larger bars become more effective.

I think this statement is the most over looked issue when upgrading to a larger torsion bar. With a STIFF chassis, you can run larger bars and not effect the ride. I run 1.02" bars in my 6.1 Hemi Duster with the complete US Car Tool Level 2 Chassis Stiffening Kit and it's not stiff riding, but it sure doesn't lean into corners!