The Monaro was originally intended to be debuted in 2003, but after the go ahead had been given for the Bathurst 24 Hour to be run in November 2002, the car's build and development time shortened to just 9 months.

The aero kit (front and rear wings) on the Monaro was based on the similar aero package used on the Holden VX Commodore that ran in V8 Supercars (the Monaro road car was a 2-door coupé version of the VX Commodore), though the rear wing was larger than a V8 Supercar's and to conform to GT regulations had to be lower in height than the cars roof line.

However, due to the high cost specifications, the business case for full production failed since Holden could not built the 427 in such limited quantities for the original asking price of A$215,000.

[2] The first car was built in mid-2002 and was given a shakedown run by GRM's V8 Supercars lead driver Garth Tander at the Calder Park Raceway in Melbourne before it made its first public appearance when Holden Motorsport bought track time at the 2002 Bob Jane T-Marts 1000 V8 Supercar race at Bathurst in order to promote the Bathurst 24 Hour to be run later in the year.

In its race debut at the 2002 Bathurst 24 Hour, the #427 Monaro was driven by Tander and fellow V8 Supercar drivers Steven Richards, Nathan Pretty and Cameron McConville.

Although Holden cars had a strong reputation at Bathurst and the similar engined Corvette C5-R's had scored numerous class wins in GT endurance racing, the Monaro was seen as too new pre-race and wasn't really considered a chance of winning or even finishing its debut race despite the relatively low quality of the field with only 3 or 4 of the 36 entrants considered a true chance for outright honours.

Then, just a few hours into the race after re-taking the lead from the Porsche, the entire fuel cell of the Monaro needed to be replaced, dropping the car 13 laps behind.

The team overcame the fuel cell problem as well as the car becoming jammed between gears just before sunrise after Nathan Pretty was hit by the BMW 318i of Debbie Chapman in The Chase, which also caused damage to the driver's side door.

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.

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.

[4] Against a much better quality field than in 2002, including the Stokell Lamborghini, a new 5.0 L BMW M3 GTR V8 for John Bowe, the Ferrari 360 N-GT with David Brabham leading the driving, the Martin Short Mosler MT900R that had finished second the previous year and had since won the 2003 British GT Championship and the GTO class at the 2003 1000 km of Spa (finishing 6th outright), as well as numerous international and Australian Porsche 911's of various specifications, it was the Brock Monaro which won the 2003 Bathurst 24 Hour with V8 Supercar drivers Jason Bright, Todd Kelly and Greg Murphy sharing the driving.

After easily qualifying 1-2 with Tander claiming pole with a time of 2:13.2856 (the fastest ever Monaro and Nations Cup time around The Mountain), 2.7 seconds faster than Murphy in 05 and some 4.4 seconds faster than John Bowe in 3rd, the Monaros controlled the race which was run in wet and dry conditions with the rain at one point (after just a couple of hours) coming down hard enough to have the entire field of 46 cars stopped on the pit straight for almost 10 minutes for safety reasons (also due to the lightning, race broadcaster Channel 7's camera operators around the circuit were forced to stand down from their metal tube scaffolds).

The Ferrari 550 (the same model that had won the GTS Class in the 2003 24 Hours of Le Mans, defeating the Corvette C5-R's that used the same size 7.0 L V8's as the Monaro's), was powered by a 5.5 litre V12 engine and produced approximately 600 bhp (447 kW; 608 PS).

It would prove to be not only the Monaro 427C's last win, but the last ever race of the Nations Cup Championship as Ross Palmer could no longer afford to fund the series and PROCAR was disbanded after failing to find a major sponsor.

[citation needed] After their 2002 Bathurst 24 Hour win, it was expected that the Monaro's with their all-powerful (and some thought unfair) 7.0L V8's would come to dominate Nations Cup racing.

The 2003 Bathurst 24 Hour winner is currently owned by a historic car racing enthusiast, the third Monaro driven by James Brock was placed under auction on 20 February 2020.