i agree with Dphariss, heat them red hot, and insulate for at least an hour in wood ashes, or warm sand. These parts are not iron. They are mild steel, that has been investment cast. The problem is not the mild steel, its the casting process that can cause you fits. If you anneal the parts, they will not behave like annealed brass, but will be stress relieved, and less likely to break if they are annealed before bending or shaping.
Either lock will need cosmetic work to be believable on the rifle you propose. The Siler is a Germanic design, that is less believable on a southern rifle than an English style. The L&R is an English design but would require backdating to be believable. Both are fine locks, it pretty much comes down to which one you are more comfortable grinding on.
Hungry Horse