Welcome to the site.
In respect of the 'K'-class dimensions: Have you contacted N Scale Modellers Australia
(Google it)? They may be able to help, and if not, then the Victorian Branch of the Australian Railway Historical Society
at Williamstown, Melbourne would be a good alternative.
As has already been pointed-out, 'Australian N' is something of a rarity on this site (New Zealand 'N' even more-so), and as the majority of members are 'Brits' your modelling will be observed with some interest.