The design of these power steering units causes it to seem like a lot of play in the steering if turning the wheel back and forth with engine not running. I would say 1/4 tp 1/3 of a turn without engine running is normal. When you steer without engine running, the steering shaft raises up and down before wheels actually turn. When engine is running, the steering shaft still shifts up and down very slightly which opens and closes the valves and high pressure oil is sent to the piston to steer the wheels. When new, there should be very little slack in steering - less than 1/8 turn. In my experience, it has rarely been wear in parts 1 and 23. Usually the play is in bellcrank and splines in steering arm. When it is in the valve assembly, it is usually worn snap rings, valves, or in need of shim adjustment in the valves. You mentioned having splines welded up and improved steering for a while. My guess is that the splines are again getting loose. When those splines get worn it is impossible to keep the bolt tight. I have found the only reliable way to repair is to replaced the cast steering arm and usually the splined shaft as well. A small amount of play in those splines makes a lot of play in the steering wheel.