The Festiniog Railway Traveller's Guide has appeared as a number of editions over the years. Some contained information regarding the rolling stock, and specifically an edition noted with a blue cover has been used extensively in Festipedia. This edition contains a Stock List dated 1.4.1992, and Research is credited to Michael Seymour, the then Archivist of the FR, so it should be reliable. See here for this and other editions.
This needs expanding