Bourdais was penalized during the race for avoidable contact, but the damage was done.
Sebastian Buemi and 2008 driver Sebastien Bourdais will also take part in the three-day test.
The 29-year-old Bourdais had spent an anxious winter waiting while the team assessed alternatives.
Bourdais's move comes after he impressed Toro Rosso in a series of tests this summer.
Wilson passed Sebastien Bourdais midway through the race to set himself up to take his third career win.
After Power got out of his car, he threw his gloves toward Bourdais.
And Bourdais, a four-time winner of the US-based Champ Car series, admitted his relief at finally securing the drive.
Toro Rosso tested Buemi, Bourdais and former F1 racer Takuma Sato last week.
But Frenchman Bourdais, in his debut F1 season, crashed into a barrier at the Circuit de Catalunya on Wednesday.
Bourdais moved to the US after failing to win an F1 drive despite winning the Formula 3000 title in 2002.
Behind Sebastien Bourdais in his Toro Rosso, Kovalainen will start 18th, his lowest grid slot since joining McLaren prior to last season.
The Japanese racer bettered Buemi and Bourdais to set the fastest times of the three during November's test at Spain's Circuit de Catalunya.
Power's shot to compete for a win ended when he was bumped from behind by Sebastien Bourdais, a move that affected nine other cars.
German Sebastian Vettel has been promoted to the senior Red Bull team, while his 2008 Toro Rosso team-mate Sebastien Bourdais may not be retained.
Last month they dropped American Scott Speed in favour of German Sebastian Vettel with immediate effect, and now Bourdais will replace Italian Vitantonio Liuzzi.
Four-time Champ Car title winner Bourdais was eighth quickest of the 10 drivers in action, with a best lap of one minute 20.715 seconds.
The two Toro Rossos of Sebastien Bourdais, who shocked the field by leading the first qualifying session, and Sebastian Vettel rounded out the top ten.
Bourdais hopes to retain his seat after the departure of team-mate Sebastian Vettel, who claimed the team's first victory at the Italian GP, to Red Bull.
Frenchman Bourdais, who won the first four races of the season, heads goes to San Jose, California, for next week's event leading Wilson by 23 points.
Dietrich Mateschitz, who owns both teams, revealed Buemi was "very likely" to be chosen, which would leave Sato and Bourdais to fight it out for the other seat.
Bourdais was overshadowed for much of last season by former team-mate Sebastian Vettel, who has been promoted to the main Red Bull team alongside Mark Webber for 2009.
The 27-year-old saw the race restarted with 16 laps to go, but moved clear once the action got going again to beat Bourdais to the line by 5.319 seconds.
Bourdais becomes the latest driver to try to convert success in the States to the much more demanding world of F1, a career path that has proved to have mixed results.
Toro Rosso's Sebastien Bourdais was classified seventh on an impressive debut following Barrichello's exclusion, despite retiring with engine failure while running fourth ahead of Alonso and Kovalainen with three laps to go.
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Toro Rosso, who have not scored any points so far this season, have yet to name their second driver for 2008 amid speculation that triple ChampCar champion Sebastien Bourdais could replace Vitantonio Liuzzi.
Nico Rosberg completed a disappointing afternoon for Williams as he failed to take part in the second session, which saw the Toro Rosso duo of Sebastien Bourdais and Sebastian Vettel also eliminated along with Red Bull veteran David Coulthard and Honda's Jenson Button.
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