No matter how good the castings are, working up a lock from castings is a LOT of work. I think the production guys(ie: Chambers, L&R, etc) have drill fixtures, mill fixtures, special collets to hold tumblers in the lathe, etc. I have some of Jack's castings and like them so far. I have not assembled them yet, but the look entirely workable. One thing I like is that he sprued up the waxes with heavy feeders, to avoid sinks on the castings. These are a pain to clean up, but far better than having to weld a sunken spot up.
If you've never built a lock from castings before, I'd suggest starting with a large Siler kit, as they go together pretty easy compared to a TRS or Brooks.
I would research this site for topics on the subject. It's a huge task to describe step at a time how to do it. Perhaps getting your hands on a Siler instruction sheet would also be helpful.
Acer