The Old Army gripframe will bolt right up to a Vaquero, Blackhawk, single-six etc HOWEVER. It is only a direct interchange with an Old Model
(3-screw) blackhawk or Single-Six. The trigger spring is different, it is a coil and plunger in the guard behind the trigger.
In the New Model (Vaquero,etc) the trigger spring is a long torsion spring hung off hooks in the gripframe. You can convert a New Model guard to fit an Old Model by making a filler block with a trigger spring hole to fit in the trigger slot, but for the reverse conversion you would have to machine away material on the Old Model (Old Army) gripframe to let the front of the torsion spring in, and install the pin in the back of the frame for the legs of the NM spring.
If you use (as many have) an Old Army gripframe on an Old Model Blackhawk (The Stainless Steel is pretty, and heavier than the aluminum one) all you need is a SBH style wide trigger. Hard to find. A 3-screw SBH conversion trigger will work if you grind off the arm that actuates the hammer block. Unfortunately, Ruger will not sell an Old Model trigger to you, unless they fit it, which they won't if you are modifying things....
