Don is "on the money". Start by VERIFYING exactly where the play is.
With engine off, have an assistant turn the steering wheel back and forth while you look underneath for play in any of the steering components, including the bell crank. The assistant should turn the wheel in large enough arcs that it JUST starts to move the driver's side wheel. Then the right side wheel. That way, you can tell if there are worn components OTHER THAN the steering box involved.
And, yes, more caster will give you better "return to center", but is really not a cure for play in the steering.