First off, you should ask your son just what he has in mind when he said he wanted a "Cowboy" gun. To most people, that is simply a Single Action revolver.
When I think of a "Cowboy" gun, I see in my mind Roy and Hoppy, Mat Dillon and Doc Hollidy and the guns they carried.
Rugers are the workhorse of single action revolvers, built like a tank and will give years of service, but I never ever seen Doc cary a revolver with adjustable sights, or Gean or Roy, either.
When I think of a "Cowboy" gun, it's a Single Action revolver with fixed sights in 45 colt caliber. That's the picture I see in my mind and you should get it from your son just exactly what he's thinking of before buying one.
The Ruger Blackhawk is a great cary and hunting gun, but it ain't no "Cowboy" gun with them big sights setting up there in the way and spoling the clean lines of a great SA.
Greeenriver