Torsion bar needs will widely vary based on balance of the car, BB, SB, A-body, B-body, etc. The 1.03 are a good all around rate as it matches up to the compression and rebound settings of the Bilstein shock they offer. You go to a bigger bar you run the risk of over working the shock and hurting it.

At that point, as we do on our car which has 1.12 bars in it, you must consider going to more race type adjustable mono-tube shock.