Ford last week confirmed the 2020 Mustang Shelby GT500 will pack 760 horsepower when it arrives at dealerships in the fall.

However, an Australian outfit, led by retired racer Dick Johnson, has gone one better. It's preparing a Mustang with as much as 850 hp.

Johnson revealed details of the project the same day Ford announced power numbers for the Shelby GT500. He said the car is being developed with Rob Herrod of Herrod Performance, an Australian tuner specializing in Ford products. He also said all build slots have been sold.

Johnson, who is the co-founder of DJR Team Penske, which competes in the Australia Supercars touring car championship, has launched a handful of Ford specials in the past. These were based on the locally developed Ford Falcon sedan, with the last, the DJR 320, presented in 2003. It had 435 hp and was limited to just 14 units, and it was also developed with Herrod Performance.

Herrod Performance offers a number of upgrades for the Mustang, including items from Ford Performance, Roush and Hellion Power Systems. One of the Hellion kits listed on Herrod's website is claimed to be capable of more than 2,000 hp, which makes even 850 hp look mild in comparison.