how much trouble to....

change from manual steering to power. car I am looking at has a 400 BB in it, but the steering leaves a lot to be desired. manual box. I looked around and it seems that power steering gear boxes ain't cheap; then I have to get the pump/reservoir and find a bracket to mount it. supposed to be a new box, but there is a not of play before it "catches". I know it's not rack and pinion, but I didn't remember it being so loose.