Bill, if you are building from a board, and have not cut the wood down to near its finished size, you can likely get away with inletting the barrels and breech tang. I hope you have a drawing of the full sized thing...I wouldn't leave anything to chance, and just hope it works out. Your best bet for a successful build it to wait 'til you have the pair of locks you'll be using, in hand. Then add them to the drawing. Then shape your stock. Conversely, if you use TOW's catalogue and order the locks from them, you can make a tracing of the lock complete, and add it to your blueprint. then you'll be very close when you finally acquire the locks.