The tangs on a low wall are a bit thinner, making it just a tiny bit different than a high wall. High wall can be made to fit, but not going the other way. Well, it'll fit, but the metal will be sticking out  in a poor looking way. 
If the action is one of the final Winder muskets, the High wall stocks will fit, because they have the larger dimension. They are generally thought to have been high walls with the "ears" removed.