Your carb is a 'model' 4160 unless it has been altered. The only difference between Models 4150 and 4160 is the use of secondary metering block instead of a plate. Model numbers are more like families of carbs with similar characteristics.
A "List Number" 3310-2 through -6 and a list 1850 are both 4160s but have different gaskets, floats and probably some other parts.
