Any earlier style rifle with a cheek piece will require 2 1/2" minimum of clean wood for convenient work an early Dickert is hard to make without 2 3/4" For some late half stocks without cheek pieces or very trim mountain rifles one could get by with a full, clean 2" if you were very careful on layout. Both of these thickness would be for a hand built stock, if the stock is to be duplicated it will have to be thicker to start with. While most of us like to be cheap and go find stuff to use, it really makes little sense to not buy an appropriately dried, ready to use blank from one of the stock blank guys as the plain pieces of wood are really inexpensive.
Tom