How much difference will it make?

I'm more of a autox / wannabe road race guy. So your question about the Torsion Bars is yeah my understanding the trick is you are going to want to back to the original v-8 bars or even get a set of slant 6 torsion bars if you want to drag race it. The reason being the 1.03's are thicker and keeps things planted on the front weight of the car. The slant 6 bars are thinner/smaller and will lift / shift the weight load on the back tires getting you more traction...