The conversion to .45 Colt required a taller front sight. The holster is an El Paso Saddlery tanker holster. The short barreled gun is a .44 magnum.
Exactly right. The .45 Colt is a much slower round (though in your F/A it can be made to just about equal the .454), and it impacts higher on target than the .454 with the stock front sight for the .454.
That EPS tanker holster is the exact same one I am getting for mine after I get it shortened to 6".