rail for ruger 4.2 inch redhawk

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I need a rail/mount for a 4.2 inch ruger redhawk- the one with the PINNED front sight , not the one with the plunger type, although I have seen both- as to whether that plunger type is factory or replaced, I don't know - all I know is that I need to scope this pistol or red dot it as my eyes don't focus that well anymore