A C3 Corvette spindle is approximately 1" taller than a 55-57 spindle. But it also has 7º of steering axis inclination compared to a 55-57's 3.5º. The extra height of the spindle gives you a favorably different camber gain curve. The extra steering axis inclination is better suited for wider wheels and tires, as it reduces the scrub radius.
You can put a C3 Corvette spindle on a 55-57 by making a spacer bushing for the lower ball joint pin, and shortening the upper control arm about 3/4". It also lets you run the C3 12" rotors. Down side is that there's no dropped spindles available.
A tall upper ball joint would get you the camber gain.
The reason for the camber gain is primarily from having the upper control arm having the ball joint higher than the control arm's shaft.