"Wild Bunch" is predicated on the guns of the Mexican Revolution used in the movie. Hence the requirement for a 1911 and the '97 shotgun. Your rifle/carbine must be .40 calibre or larger, which means 38-40/44-40/.44 Spl./.45LC.
What I like about it that it is the closest CAS gets to having a realistic power factor. I suppose you could put limp springs in a 1911 to shoot mouse fart loads, but most also use their 1911s in IDPA/IPSC, so that isn't likely.
Some clubs go "outlaw" and admit ANY period handgun (Colt New Service, Luger, etc.) with a cut off date up to 1914 but may require the use of lead bullets only.
Sometimes I wear a 'Soldier of Fortune' outfit, all khaki, including wool puttees to the knees. My wife has done Mexican 'Soldadera' with straw sombrero, multi-coloured skirt and off-the shoulder-blouse but prefers the white shirt William Holden look with black ribbon bow tie. She shoots "Modern" - two hands with an SR1911 using her IPSC load.