* 2.76: This was a common ratio for better fuel economy.
* 3.23: A more popular all-around ratio offering a balance between performance and fuel economy.
* 3.55: A more performance-oriented ratio, better for acceleration but slightly reducing fuel economy.
* 3.91: A higher performance ratio, providing strong acceleration but at the expense of fuel economy. This would have been more common with cars ordered with performance options.
To know the exact ratio in a specific 1973 340 Duster, you'd need to check the vehicle's build sheet (if available) or the axle itself (the ratio is usually stamped on the differential housing).
