I believe it's an Allard J2X Le Mans, 1952
(Does it have the Chrysler hemi in it)?
The Allards ran 5.4 Cadillac V8s, Sydney came 3rd in a J2 in 1950, but thats looks like a Bristol from a few years later. 2 litre class winner
Whoops, had to look it up, as the numbers started with the biggest engine, so that must be something with the sixth biggest engine, so the Allard J2X must have had the same coachbuilder as Bristol in 1954
And the following year, Hawthorn & Bueb won in No 6