A Birdshead is nothing but your XR3-RED/ "Plow" that is round butted.
A Bisley Hammer and/ or a Trigger can be used if you seek those particular attributes,,,ie Wide Lower Hammer Spur and extra Curved Trigger,,,
The Bisley hump will need to be removed and some of the Trigger will need a slight trimming.
I personally like the Bisley Hammer, and compare the 2nd gun Trigger to the others to see a Bisley Curved Trigger -vs- Standard.
The rest of the guns have a standard trigger,,,
that I like to thin a bit and remove a good portion of the backside web,,, all in a effort to make the Standard trigger look more streamline,,,IMO the standard Trigger can look "chunky".