The rear sight assembly from the GP100, Redhawk, SRH will fit on a Security Six. The front sight will not. The front sights on the Security Sixes are pinned, unlike the GPs, Redhawks, etc. with adjustable sights. They have a unique quick-release front sight that is locked in place by a spring and plunger system at the end of the barrel.
There are several current DA Rugers that use the pinned front sights, 4" Redhawk, 3" GP, Alaskan, SP, etc.., but I'm not sure if they will fit in the Security Six.
Maybe someone will chime in with some more information about the pinned front sights on the Ruger DAs.