If the new cylinder stop doesn't have a hole for the spring, you either have the wrong cylinder stop or a defective one. The other possibility is that you have a five screw revolver, and the cylinder stop spring is in a cavity behind the additional screw in the front of the trigger guard.
I believe yours was built after the trigger guard screw was eliminated so perhaps you have the wrong era cyl. stop??

By the way, the cylinder stop and the new hammer are not considered "drop in" parts and will likely need fitting.

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Ret. LE, FA Instr, S&W Armorer