Some additional notes:
Original K1 and K1a smokeboxes weren't so much welded as flush-riveted. That is to say that, once applied, the rivet heads were blended into the sheet metal of the smokebox. They would not show in photos.
Once the GSR/CIE overhaul scheme was underway and the smokeboxes fell to be replaced, standard practice was to use snaphead rivets whose domed heads were clearly visible. They were somewhat cheaper in terms of labour costs to use. The Maunsell door was also replaced by the GSR style (similar to the SECR Wainwright type which was part-domed, part-flush) with a wheel-and-handle.
The Irish engines also had a wider overall width over their footplates: I forget if it was 8'9".
Both K1/K1a shared the same 7'3"X 8'3" wheelbase, as did the British "N", but the 6' wheeled "U" had its own 7'3" X 7'9".