https://collection.sl.nsw.gov.au/digital/qkPWlp5rDep35 I'm hoping the link takes you to the 20 photos of this event. It does look staged. I think there were at least five cars 'racing'. The library doesn't seem to have anything other than the photos, the photographer's name and the publisher. On the library website you can enlarge the photos to see quite a bit of detail. The car in photo 10 (the middle car in the group photo I posted) has a supercharger. [Stueeee - you appear to be correct in mentioning the MG Y: a Y rocker cover in an internet image looks just like the rocker cover of the supercharged engine.]
'Bathurst races 30 March 1959' [NHRA sticker (transfer?) on cowl] Mitchell Library/State Library of New South Wales
(Austin 7? I like the megaphone exhaust.) 11th Rob Roy Hill Climb, 24 Nov. 1946; George Thomas photo; State Library of Victoria
Photo possibly from the Kyneton area, Victoria, Oz; by Vincent Joseph Hearnes 1903-1986; State Library of Victoria. Is this based on a Ford or something else?
L. Little and E. O'Keefe's racing car outside their garage in Whitehorse Road near Pratt Street, Ringwood, 1925 (Ringwood and District Historical Society) [Melbourne, Oz]
'J. Spence driving an Austin Special, AMSC Standing 1/4 mile' [1946] George Thomas photo, State Library of Victoria
'Chamberlain Special on the starting line, 10th Rob Roy Hill Climb' [1946 photo by George Thomas; State Library of Victoria] When I saw photos of what must be a two-stroke special I thought I had made an important discovery ... but it's all been discovered before; I am fairly sure there are previous posts in this thread about the Chamberlain 8. Anyway, here are six photographs and a link to a long article (2 articles, I think) on the fantastic 'primotipo' website (which I am still to read). https://primotipo.com/2015/07/24/chamberlain-8-by-john-medley-and-mark-bisset/
H. Hawker driving a Chamberlain Special, 16th Rob Roy Hill Climb, 1948; George Thomas photo, State Library of Victoria
Ned Ludd - does the Cyclecars thread have something on the earlier Chamberlain? That might be where I have seen it.
One of my all-time favourite specials, the Lion W-12 engined 1932 Napier-Railton https://oldmachinepress.com/2020/03/05/cobb-napier-railton-endurance-racer/
Diana Davidson, 16th Rob Roy Hill Climb, 1948; Austin 7-based? George Thomas photo; State Library of Victoria