Frenchy and Wazza are driving to Townsville, via Birdsville, from Melbourne - in a 1996 Camry.
John French and Warwick Noon, as the Mountain Mungos team, will be part of this spring's Shitbox Rally.
The rally raises money for cancer research.
Frenchy said the death of his brother-in-law from brain cancer spurred him into action.
"It had a tremendous effect on our family. It was out of the blue - diagnosed in the February and died in June," he said.
The family actually inherited his car so put their old bomb on Gumtree.
"This bloke rang up and said, I want to buy it, sight unseen," said Frenchy.
When they discovered why he wanted it - for a Shitbox Rally - they gave him the car.
It was then he decided he wanted to take part himself. He teamed up with Wazza, who has a family member battling neuroendocrine cancer, but the pair had to spend two-and-a-half years on the waiting list before the Mountain Mungos won a spot this year.
Frenchy, a taxi driver from Katoomba, and Wazza, who runs Advanced Auto at Leura and lives in Bullaburra, paid $300 for their 1996 Camry, which was destined for the wreckers.
Some youths from Mountains Youth Services Team painted it and the pair are now preparing for the October start in Melbourne.
They have already been fundraising and have raised almost $9,200 so far. They are aiming for $10,000.
Their latest fundraiser is an exhibition of large-canvas photographs, largely Frenchy's work with native birds, at the Katoomba RSL Club on Saturday, August 31 from 2.30-5pm.
Tickets ($20/$15/$10) get admission to the exhibition, a welcome drink, finger food, lucky door prize, live music and five tickets in their mega-raffle.
Shitbox Rally is the Cancer Council of Australia's major fundraiser. Since it was launched in 2009, it has raised more than $20 million for research.
The rally is not a race, rather a reward for fundraising efforts, according to founder, James Freeman.
"This is a chance to explore Australia, drawing teams from around the country to help achieve the extraordinary.
"Shitbox Rally 2019 Spring will ... take us through parts of drought affected outback Australia, so we can add revenue back into the community. Heading north, the terrain and landscapes will change dramatically each day.
"It will be an iconic rally with some exceptional stopovers before our final 10-year party in Townsville to celebrate the conclusion of one huge year."
To donate to the Mountain Mungos, see https://2019spring.shitboxrally.com.au/mountain-mungos.