New engines that will be produced at General Motors’ Town of Tonawanda engine plant will go into new versions of the automaker’s top-selling Chevrolet Silverado and GMC Sierra trucks, as the manufacturing complex continues to step up its employment.

GM officials announced their plans for the new trucks Thursday, as well as GM Tonawanda’s prominent supporting role. The Tonawanda complex will be the lead supplier of three new engines for the trucks, as well as the only GM plant that produces all three of them, said Mary Ann Brown, a spokeswoman for the Tonawanda facility.

The engines, which will go into production in the first quarter of 2013, are part of a $400 million investment in GM Tonawanda announced in 2010. The plant is now seeing the payoff in the form of new jobs, as well, as it staffs up to fill new positions that were projected with the new work.

The plant currently has about 1,100 hourly and salaried workers. That total is expected to rise to 1,600 to 1,700 over the next year, as Tonawanda’s new engine lines enter full production. GM workers transferring from other facilities have the first opportunity to fill the new positions.

GM recently announced that the Tonawanda site would be the exclusive supplier of a V8 engine for the next-generation C7 Corvette. And earlier this year, the plant launched production of new Ecotec four-cylinder engines for the Chevrolet Malibu and Cadillac ATS, stemming from a separate, $425 million investment.

The new engine family for the Silverado and Sierra includes a 5.3-liter V8 and a 6.2-liter V8. It also includes a 4.3-liter V6; a new V6 had been a source of speculation at the time of the 2010 investment announcement but was not publicly confirmed by GM until now.

“They’re giving customers three different options to choose from,” Brown said.

GM is aiming to get its new Silverado and Sierra into showrooms by late spring or early summer. The timing is good. Truck sales are growing after a five-year slump amid the economic downturn. And the new pickups replace models that were last revamped in 2007. That means GM dealers are offering pickups that are dated, compared with newer Fords and Chryslers, and it is hurting sales.

GM says the 2014 trucks should put the company back in front. The trucks look a little more aggressive and aerodynamic. They will have quieter cabs, and updated steering, suspensions and brakes, GM says.

Gas mileage and pricing of the trucks was not released, although GM North American President Mark L. Reuss says customers will be surprised by the prices. He says the trucks are 200 pounds lighter than Ford and Chrysler competitors, which will help boost gas mileage.

The trucks should close the gap with Ford’s F-150 and Chrysler’s revamped Ram, especially if the engines are more powerful and efficient, says Jeff Schuster, senior vice president of forecasting for LMC Automotive, a Detroit-area industry consulting firm.

“The focus that they really put into these trucks, I think, gets them there,” he said.

Full-size GM pickup sales fell by 8 percent last month, while competitors saw increases.

At the end of November, GM had enough trucks on dealer lots to supply them for 139 days of sales. A 60-day supply is considered optimal.

Reuss says GM raised incentives to match competitors, and sales in early December are strong. The company didn’t offer big deals last month, and it hurt.

Reuss says GM intends to outsell Ford’s F-Series, which is the top-selling vehicle in America, but he would not put a time frame on reaching the goal.

The Associated Press contributed to this report. email: