Steering All Over the Place at 55mph+

Caster goes negative as the suspension rises. A car 2" higher than stock in front will surely be at zero or negative caster.
A car with a rake....where the rear is much higher than the front will also have very little if any caster.
The upper ball joint needs to be rearward more than the lower ball joint to have caster. The higher the rear of the car, the less caster will occur.
The worst is a car that is jacked up in the rear and the front.