1971 Dart Swinger Steering Gear Adjustment needed.

Could someone tell me what aspect of the steering box adjustments can remove the free travel that I feel when driving down the road in a straight line but having about two inches of side to side free travel in the steering wheel. Aside from the play in the wheel once engaged turning left or right is very smooth, but keeping the car centered in the lane is a challenge. Also when looking on line at a replacement steering box I see two common choices 24:1 ratio and 16:1 ratio. Does this determine how quick your wheels turn in relation to how much you turn the wheel? Will either one fit my car without changing several parts? Which one came on the car from the factory?

Thanks.

This should explain what you asked.
(If that is where the play is)