[Flieger]

This is before studying the spreadsheet posted above:

Well, by my calcs, the motion ratio for the front anti-sway bar* (*=aftermarket) means it twists about 108.4% of the torsion bar for a given wheel displacement, so the motion ratios are pretty close.

If the sway bar is measured in # per degree, that usually means that half of that degree comes from one wheel, and half from the other. The torsion bar being measured in # per degree means that all of that degree comes from one wheel. This means that for a given wheel displacement, the sway bar contributes twice as much force as the torsion bar, or that the front sway bar contributes 2/3 of the front roll stiffness.

Torsional stiffness # per radian is JG/L
J=(pi/2)r^4
G is about 11600000psi
effective L for the sway bar is about 36 inches
effective length for the torsion bar is about 22 inches, IIRC.