Adjustable vs. Non adjustable kickdown rod

So I have a non adjustable kickdown rod from a 75 dart with a 318 and the one on the engine is a 72 dart with a 318.

Is there any advantage to having an adjustable one??

Does anyone know when they went to the non adjustable, which one was used in 1974?

They seem to be the same size and angles but one is adjustable and one isn't.

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