Leakless Water pump

[Diastole]

I am preparing to change my radiator. As I read I notice that the vendors say the "impeller should be cut-down" to slow the flow rate and prevent overflowing. And, this is required for reproduction radiators.
So the level of fluid and the flow rate seam to matter as well as the baffle.
Question I have is, if I change my radiator, should I change my impeller, too? My original water pump works well, has no issues, isn't leaking.