Just to show you how much variation one might find in Ruger Blackhawks, here is one of my New Model Blackhawks. It has the Super Blackhawk (Dragoon) style steel grip frame, and a non-fluted cylinder, as this was once a Bisley:
And this three-screw Blackhawk .44 Special was once a .357 Magnum, now has a steel grip grame.
And here's a couple of my three-screw Supers pretty well stock except for fitted with Blackhawk hammers, which I prefer. Bottom gun with brass grips frame, top one has been case hardened.