In 2003 GRM built a second car for the legendary touring car driver Peter Brock which would make its on track debut in Round 2 of the championship at Symmons Plains in Tasmania. Brock had driven the Bathurst winning Monaro at the Nations Cup support races at the 2003 Australian Grand Prix in Melbourne before the start of the championship a few weeks later in Adelaide. In Melbourne the car ran with Brock's famous #05 rather than its usual #427, winning all four races after battling with the Lamborghini Diablo of Paul Stokell, though Brock admitted that he would not have won any of those races had Stokell not struck trouble in each race. He then drove the new car, painted red and, until late in the series, without the Monaro teams sponsorship of Just Car Insurance (GRM's usual major sponsor in V8 Supercars was Valvoline), in the Nations Cup Championship alongside Pretty, though he did not win a Nations cup round or race until the opening race of the final round at Surfers Paradise. Pretty and Brock finished third and fourth respectively in the 2003 championship.