Indeed, Darren, I couldn't agree more.
This, of course, is what the IRRS is for. If you are a member and have convenient access to their archives in Dublin, you will find a treasure trove of all sorts of old archive material from track plans to timetables to borardroom minute books. Station architecture, rolling stock drawing and other material feature too. You will find the resident archivists, Herbie Richards and Tim Moriarty, extremely helpful. As a member, you can access their online photo archive, a rapidly growing and massively important archive of photographs, which has been created by their photographic archivist, Ciarán Cooney. He continues to add new stuff to this, as time permits it to be digitised.
I would highly recommend membership for all of the above reasons and more - monthly historical talks and presentations being another.
Members Richard McLachlann and Herbie Richards have over the years compiled a number of invaluable publications of stock lists, original rolling stock drawings - plus some GNR architectural drawings; in fact, a copy of this latter was amongst the stuff they had for sale at Raheny!