A good link for the local Western Australian Sn3.5 group is
http://wasnmodeller.blogspot.com/, and shows what a large selection we have down here for models from the late 1870's through to around the 1970's (not much for the later periods, as the local prototype went to unit trains during the 1980's, general freight fell away, etc).
I am now working on the same type of thing, but using TTn3.5 (3'6" gauge on 9mm N gauge track), as I have very little room for a layout for the larger Sn3.5 models.
Cheers,
Matt