Hi,
I'd concur with what Bill offered and add that spring rates (torsion bars, in this case) should be chosen by taking into account several factors.
1) Vehicle weight
2) Wheel/tire package
3) Driver skill, experience, and preference (this is huge)
4) Engine power
5) Usage: street-only, street & track, racing
This is NOT a one-size-fits-all sort of proposition and there are many different solutions tailored for each individual.
