Khe-khe... I saw these photos. The first photo shows military parade at Lochinvar, N.S.W. (Date of creation: [ca. 1940], State Library of Victoria). The trucks are something old-fashioned (exactly not Ford Marmon-Herrington 4x4

) while modernized 18 pdr MkIV guns look nice!
The second one shows artillery practice at Sandringham by 18th Heavy Battery (Date of creation: [ca. 1932-ca. 1938], State Library of Victoria). The tractors are Thornycroft "Hathi", it's clear, while the guns seem to be 6 inch howitzers... However I'm not sure that they were used for towage of 3inch AA trailers for some reasons (at least because only a few "Hathi" tractors (possibly seven) were supplied to Australia in the early 1930s...
Leonid