To answer your question: "Are there different tolerances for different year manufacture?", NO & YES. Basically the manufacturing year is irrelevant. These guns are not sold as "switch barrel" guns. To get a second barrel the frame needs to be sent back to factory OR personally fit to the new barrel to that frame. NEVER alter the frame itself.
Either barrel could likely be fit to either receiver, but doing so will eliminate that barrels ability to be mounted to its original frame. (at least with out adding removed material)
CW