Carter 4640SA Date Code Question

66fs said

It is a 69 440 HP automatic carb for B and C Body cars with and without AC. One of the best carbs ever made. The date code is April 1971 when it was manufactured. "S" means it is an assembly. "A" means it has been revised once.

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I’m leaning towards the idea that the “SA” is an “over the counter replacement”. I have six 1969 carbs stamped “SA” and the build dates (years) are all over the place plus I have a few 1968 carbs with just an “S” that were stamped with an “8” indicating that they were built in 1968.