More info from the RAAF Museum Point Cook Facebook:
The RAAF Museum has recently taken this KS5 International Aero Engine Test Truck on loan for use with the Museum’s second Merlin engine.
The truck, which was built at the International Harvester Works at Geelong in 1941 and acquired by Australian National Airways, was originally used as an aero engine test bed for R1820 Radial engines after they were overhauled. Those engines were subsequently used in support of US B17 bombers and DC3 aircraft at the beginning of WWII. It became the property of Ansett Airlines after its takeover of Australian National Airlines (ANA) and was upgraded to test run R2000, R2800 and Bristol Hercules engines until the 1970s when Ansett ceased to operate piston engine aircraft.
Subsequently, the truck had a succession of owners until it was acquired in 1990 by Mr Bob Eastgate and brought to Pt Cook for refurbishment. The control cabin was rebuilt. The engine, gear box and systems were overhauled and the truck was converted to run V12 aero engines as well as radial engines. The first Merlin engine was successfully tested in 2004.