It holds the road better. It helps make up for Mopar's "loose feeling" power steering. I don't have much caster on my 66 (manual steering) and it is still a little tough to maneuver at low speeds.
I have a 20:1 manual box on mine... couldn't find a pump/brackets for cheap so just got a new manual box.. prolly shoulda went 24:1, just won't try to turn when going slow :)