Proturing or roadrace rear suspension

Yep.

The 68 Valiant that Lilcuda now owns was as fast at Portland International Raceway at C6 Z06 Corvette. It's got leaf spring and torsion bars.

The builder/owner (Tim Werner) would scoot down the straight at 160 mph. And the car still could have used some fine tuning and has since got added advancements now like better oil pan and adjustable splined front sway bar.

If I had that 68 Valiant, the car would be much more capable that my skills.

Spot on......people SERIOUSLY underestimate the design of the torsion bar/leaf spring combo.