Mostert's current chassis, the first Holden he raced in his career, is the latest Walkinshaw Commodore to be put up for a pre-sale, with an online listing now live through Lloyds Auction.
Bidding will end on October 16, the Friday before this year's Bathurst 1000.
As with previous WAU auctions, the new owner won't take immediate delivery of the car. Instead the team will continue to use it until the end of the 2021 season before it is handed over.
It will come as a rolling chassis fitted with 2020 specifications parts including suspension and uprights, wheels, tyres and exhaust system.
The new owner can choose any livery from the 2020 and 2021 season and will also get six hot laps, GA and paddock tickets to all Supercars events in 2021, signed panels and hospitality at the 2021 Bathurst 1000.
“It’s extremely exciting to once again be offering the opportunity to purchase a Supercar to the public, especially one that will go down in the history books,:" said team principal Bruce Stewart.
“We were the first team in Supercars to offer the pre-sale opportunity, and after the success and interest it generated, we are delighted to do it again through a known and trusted auctioneer in Lloyds Auctions.
“To own a Walkinshaw Andretti United-built and prepared car is a rare opportunity, but to own Chaz Mostert’s first with our team, and then have the opportunity to watch it compete in the Great Race a few days later, is very special.
“Not only that, but the added benefits mean the owner will be part of the team, as their car takes the track in 2021.”
WAU has pre-sold two cars over the past two years, Scott Pye's Albert Park race winner and the final Walkinshaw car to take victory in Holden Racing Team colours.