Kammala jumla mai zuwa: Brock kuma ya tuka Holden Monaro 427C don Garry Rogers Motorsport (GRM), ya ci nasara hudu daga cikin tsere huɗu a cikin abin da aka yi tunanin zama bayyanar ɗaya a cikin tseren tallafi don
Babban Gasar Ostiraliya ta 2003 a Melbourne. Wannan ya sa ya tuka Monaro na 2 wanda GRM ya gina kuma ya gudanar a gasar cin kofin kasashen Australiya, gasar tsere ta GT don gyare-gyare da motocin titin ban mamaki a 2003 kafin ya kafa tawagarsa don kansa da ɗansa James a 2004 (tare da Monaros da GRM ta bayar). Ya sami nasarar nasara ta goma a Bathurst a shekarar 2003 a Bathurst 24 Hour, lokacin da ya ci nasara, tare da Greg Murphy, Jason Bright da Todd Kelly a cikin GRM Monaro, wanda aka yi jayayya da shi ta hanyar injin 7.0L 427 cui V8 maimakon 5.7L Gen III kamar yadda aka yi amfani da shi ta hanyar samar da Monaro CV8 (rikici ya fito ne daga babu wata mota a gasar cin kofin Nations da za ta iya gudanar da injin da ya bambanta da samfurin samarwa wanda ya dogara da shi. Gwarzon gasar cin kofin kasashe uku Jim Richards ya yiwa Monaro lakabi da "Kyakkyawan V8 Supercar" lokacin da ya fara bayyana a 2002 Bathurst 24 Hour).