Brown, who leads the Supercars championship by a massive 136 points over Triple Eight teammate Broc Feeney, admits he's still pinching himself after landing a NASCAR drive.

"Yeah, my used car sales numbers are going down so dad might be a bit angry at work without a seller, but there’s been some great opportunities coming up," Brown told AAP.

"It is a little bit surreal. It’s probably only just starting to settle in but I think I won’t really notice until I hit the track."

Brown's Triple Eight predecessor and three-time Supercars champion Shane van Gisbergen will act as a spotter over the weekend.

Van Gisbergen, who races full-time in the second-tier Xfinity Series, famously took the chequered flag in Chicago to become the first driver in 60 years to win on their NASCAR debut.

Asked if he intends to do the same in Sonoma, Brown remains realistic about his chances.

"I don’t feel any pressure to replicate that. It was pretty special what he did there," Brown said.

"Not to take anything away from him but that was a straight track that was something new to those drivers.

"It was a track that they’d never competed on before whereas Sonoma is a track that the NASCAR drivers are very familiar with.

"To finish is a big goal, but if we can get a top-10, that’d be a good day."

Brown won't be the only Supercars driver making their debut in the series, with Tickford Racing's Cam Waters going behind the wheel of the No.60 FK Racing Stage 60 Ford.

Waters was 35th in the 38-car field during practice, surviving a wild spin after hitting the dirt near the first turn.

"It’s a bit of an odd one because we are in two different teams so it’s whoever gets the set-up the best," Brown said.

"We would both like to beat each other, there’s no doubt about that, but right now I’m not focusing too much on that side of it."

Qualifying gets underway from 8am Sunday (AEST) while Monday's 350km race begins at 5.30am (AEST).

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