The upgraded Cleveland V8 in the 1971 XY GTHO Phase III produced an estimated , although Fords official figures for this motor were much lower. The 750 cfm Holley carburettor of the XW GT-HO Phase II was replaced by a 780 cfm Holley, along with numerous other performance modifications. The Phase III was Australia's fastest four-door production car and possibly the fastest four-door sedan in the world at the time, with a top speed of 141.5 mph (227.7 km/h). Power figures are still debated today, as Ford still claimed as the standard 351 Cleveland V8 in the GT though the GTHO Phase III received many modifications to increase its reliability and race performance. In 1972, Ford made the 15 in Globe 'Bathurst' alloy wheels available as an upgrade to the GTHO Phase III.