To use the stocks I've seen, the pistol not only has to have a extra screw head protruding out of each side of the frame, but it needs a notch cut into the metal part of the butt end of the grip.
I've always heard these pistols refered to as "4 screw" frames and, no, there are a lot of replicas that don't have both of these features.
The two screw heads catch on the inside of the metal part of the stock, and a hook and screw attaches into the notch in the pistol butt to lock everything together.
I've always thought I wanted to buy one of these stocks for my 1861 Colt (which has the needed attachment features), but the owners of these always seem to think they are more valuable than I do. ::