It sounds like you are talking about the dragoon style trigger guard on the Super Blackhawk, couldn't be sure. If you are, its a cast steel frame. Here is a photo of one I modified many years ago and it was so easy on the hand. Afraid it calls for cutting and welding. I did this 40 years ago, so I used silver solder. Today I would probably choose TIG.
You did a nice job of rounding up that trigger guard too.
The long Super Blackhawk grip suits me as well as anything Ruger ever produced, but like many here I don't like the square trigger guard much. If can find a Hunter model grip frame, it has the Super Blackhawk grip with a round trigger guard. The Hunter model itself is fine, if you like an ugly scope rib on the barrel of your hogleg.