More positive wheel centering force from the car itself, stronger feedback at the wheel, and more straight line stability, at the cost of higher steering force from the driver. These older cars were set with very little caster to make them steerable & maneuverable at low speeds and in parking lots, particularly when driven by the ladies, back before power steering was common. You presently have a lot more caster than stock, so I would try it as-is for now and see if you like it.
