Opinions on Leaf Springs and Torsion Bars?

The offset springs and shackles for the rear suggest to me that you're contemplating much larger tires for the rear than for the front. Doing so will increase understeer. Adding a front sway-bar also increases understeer, but will also combat body roll on the suspension.

Adding a good rear bar and front bar will produce a more neutral handling car. A rear bar hung from the rear axle increases unsprung weight, making the car ride a bit more harshly.

The A-39 A-body cop car had a rear bar hung from the body. It's not difficult to fabricate your own mounts and do the same.

Like BrianT, I use the Monroe gasmatics on the Demon and am pleased with them. My strategy was to go with soft springs, and stiff damping for a road car. If I were to race it, I'd change things considerably.