When building locks from raw castings you should NEVER use the cast in dimples blindly to drill your holes. Sometimes they are correct, often they are not. With TRS castings, which in my view are excellent and a joy to work with, they fill the old holes, usually above the surface of the surrounding metal, probably with clay before making the master. As a result the holes are a big indistinct, so it is better to just file them smooth and take your own measurements. I have built many TRS locks, when properly made, they are among the best sparking locks available. It also helps to follow their directions on heat treating , and not the way old Gomer at the local auto parts store says to do it.