The Daily Guardian offered a £50 trophy for the first person in Australia to break 100 mph over a mile. This kicked off a pattern for Don Harkness of putting airplane engines into big cars for big numbers on the speedometer (thanks Paul!)

Harkness built a car on a Minerva chassis powered by a Hispano Suiza aircraft engine and would set the record of 108 mph at Gerringong in October of 1925. 

Next, the Anzac was powered by a Rolls Royce aircraft engine on a Cadillac chassis, and set an official record of 128.571 mph at Gerringong.

The car was of a conventional layout and about 20 ft long built on a heavily modified and strengthened Cadillac frame and powered by a 360 hp Rolls-Royce Eagle IX V-12 engine. 

The Eagle IX was the latest and last of the Eagle line, the first of which was designed in 1915. 

Purchased as surplus from the Royal Australian Air Force, it was the most powerful engine Smith and Harkness could acquire.

The Anzac was painted gold before the Golden Arrow and Harkness painted the Enterprise to match despite Seagraves effort. 

When building the Anzac II, the govt got a bit snippy about their legalities of what the acronym ANZAC could be seen to represent, and it wasn't going to be a car, as the Australian policy stated that ANZAC can only refer to the Australian and New Zealand Army Corps 

The nearly-finished Anzac LSR car sits outside of the Harkness & Hillier Engineering Works in Five Dock. The car is missing its windscreen, seats, and gold paint. 

An additional louver was added under each exhaust stack, and the Australian flag painted on the tail would later be moved higher with “Advance Australia” written under it. Don Harkness is on the extreme right; he is looking at Norman “Wizard” Smith, who is holding one of the two black shop cats that, for a time, made the Anzac their home.

Next, the Fred H. Stewart Enterprise, of course, named for it's sponsor, after its sponsor Sir Frederick Stewart.

Despite having to redesign “Enterprise” in a hurry, the colour and shape of the cowling made it look very similar to “Golden Arrow” , so the media of the day claimed he copied Seagraves car. Despite being built at nearly the same time on the opposite side of the globe.

  It's engine’s particulars were considered secret, and the Air Ministry required a deposit of £5,000 for a Rolls-Royce engine, but when the crate was opened, it revealed a Napier engine from a Schneider seaplane  

Harkness had designed the Enterprise to use ethylene glycol chemically cooled in a heat exchanger by methyl chloride (Chloromethane or Refrigerant-40). This method would leave the car aerodynamically clean without incorporating any radiators.

It beat the world record for 10 miles in 1932 with an official speed of 164.084 mph.

https://www.thegentlemanracer.com/2021/01/gentleman-racer-don-harkness.html and https://oldmachinepress.com/2018/10/05/fred-h-stewart-enterprise-smith-harkness-lsr-car  thanks to Paul, who was also working up a story on the 'Fred H. Stewart Enterprise'