In production since the '50s, Holley 4150/4160 carbs come in all shapes and sizes. Counterclockwise from bottom left: 3310-2 750 cfm 4160 is considered to be a "universal" carb, thanks to its ...

There probably is not a mathematical formula complicated enough to calculate how many perfectly good Holley carbs have been tossed aside in favor of newer models, just because they needed a rebuild.