Penske has announced that reigning IMSA prototype champion Ricky Taylor will complete its full-time Acura line-up, with IndyCar's Simon Pagenaud and Graham Rahal confirmed as third drivers.
The team had already announced ex-Formula 1 driver Juan Pablo Montoya and Dane Cameron for one of its two cars before Helio Castroneves moved from Penske's IndyCar team to drive the second entry of its sportscar programme.
Taylor will now partner with Castroneves for the full 2018 season and Penske says his sportscar experience made him the ideal choice.
"Adding a champion sports car driver in Ricky will help our team grow and develop," said Roger Penske.
"Ricky had a phenomenal season in 2017. He brings a great deal of sports car experience and his knowledge of the cars, the race tracks and the series overall will be a big benefit to our team.
"Having that experience, along with the winning pedigree of Helio, Juan and Dane, provides a great platform as we launch the Acura Team Penske program next season."
Taylor described the Penske call-up as a "life-changing experience" after previously testing a Penske IndyCar in February.
"It was a great experience getting a chance to test an Indy car with Team Penske, but to get a call from Roger Penske offering the opportunity to drive one of his race cars full time – well, that's a life-changing opportunity," said Taylor.
"I'm definitely ready for the next challenge in my career and I couldn't be more excited to join Team Penske and work with Helio, Juan and Dane to launch the new factory Acura effort and start winning with the ARX-05 in 2018."
The 24 Hours of Daytona, the 12 Hours of Sebring and Petit Le Mans require a third driver, and Penske has confirmed its IndyCar driver Pagenaud and Rahal Letterman Lanigan driver Rahal for those races.
Pagenaud says he was keen to return to endurance racing for 2017, having earned 10 American Le Mans Series wins between 2009 and '13.
"I've been hoping for the opportunity to work with Team Penske in the endurance races for next year and I'm excited to get the opportunity," said Pagenaud.
"We had a strong first showing at Petit Le Mans last weekend and I feel like the team is on the right track."
Rahal has previously driven Acura's NSX GT car and is targeting a second overall win at Daytona in 2018 in the prototype class.
"This will be a dream come true to get to race in the Rolex 24 at Daytona and 12 Hours of Sebring for Roger Penske, someone who not only means a lot to sports car racing, but motorsports in general," said Rahal.
"I'm excited for the opportunity and I really look forward to racing the Acura ARX-05."
Penske's announcement appears to rule out Jenson Button, who expressed an interest in racing in IMSA last weekend at Suzuka, from fulfilling a third driver role for the squad, as had been suggested.