Whakaotihia te rerenga e whai ake nei: I eke ano a Brock ki te Holden Monaro 427C mo Garry Rogers Motorsport (GRM), i wikitoria i te wha o nga whakataetae e wha i roto i te mea i whakaarohia he ahua kotahi i roto i nga whakataetae tautoko mo te
Ko te 2003 Australian Grand Prix i Melbourne. Na tenei i arahi ai ia ki te taraiwa i te Monaro tuarua i hangaia e GRM i te Australian Nations Cup Championship, he whakataetae momo GT mo nga motuka huarahi kua tino whakarerekehia me te rereke i te 2003 i mua i te whakatu i tana ake roopu mo ia me tana tama a James i te 2004 (me nga Monaros i tukuna e GRM). I tutuki i a ia te wikitoria tekau o te manawanui Bathurst i te tau 2003 i te Bathurst 24 Hour, i a ia e wikitoria ana, me Greg Murphy, Jason Bright me Todd Kelly i tana GRM Monaro, i tautohetia e te 7.0L 427 cui V8 miihini kaua ko te 5.7L Gen III e whakamahia ana e te hanga Monaro CV8 (ko te tautohetohe i ahu mai i tetahi atu motuka i te Nations Cup ka taea te whakahaere i tetahi miihini rereke rereke mai i te tauira whakaputa i hangaia. Ko te toa o te Ipu o nga Whenua e toru a Jim Richards i tapaina te Monaro hei "Better V8 Supercar" i te wa i puta tuatahi ai ia i te 2002 Bathurst 24 Hour).