Consider this third-hand information at best, but....
I understand that there is a fairly wide range of tolerances to be seen over the years. For example, if you are building (for production, not one-offs) one-piece scope bases for a Rem 700, you can't just measure the distances between the four holes on the rifle action that you have in front of you. You need to find out just how much these dimensions have varied over the years, and make the holes in your base ovalled enough to fit all 700s. Not sure about other important dimensions, e.g. trigger mounting pin spacings, distance from bolt face to action face, etc.
I know of at least one stockmaker who has CNC programs for the various common actions, so that when you order one of his stocks for (e.g.) a Rem 700, he can inlet it for you without having your action on hand. This is sort of the reverse of what you want, don't know if it would be useful to you (or if this is the sort of thing that he might be willing to share freely?).