British Touring Car team Triple Eight and UK junior open-wheel powerhouse Fortec Motorsport will both expand into GT racing next season.
Ian Harrison's Triple Eight squad will partner with established GT outfit Optimum Motorsport to form a new team for British GT. 888Optimum, as the team will be known, will run two BMW Z4 GT3s from Triple Eight's base in Greatworth, Northamptonshire.
Triple Eight boss Ian Harrison said: "This is the kind of project we have been trying to get started for a few years now, and its satisfying to be finally going into it at this high level.
"Obviously, Triple Eight is new to GT racing and we do not underestimate the steep learning curve that stands in front of us. But with Optimum's experience, we have an opportunity to develop the team quickly from the start."
Joe Osborne, who won two races in British GT in 2012 in a Trackspeed Porsche, will share the team's first entry with Optimum owner and Ginetta racer Lee Mowle. Osborne's 2012 co-driver Steve Tandy will share the second car with Dan Brown, a race winner in British GT in 2009 and '10.
Mowle, who raced a Ginetta G55 in British GT in 2012, said: "Teaming up with Triple Eight will give me the opportunity to focus on racing in British GT, a huge passion of mine.
"I'm looking forward to working with Ian Harrison and Matt Kelly, and the 888Optimum team will be a great addition to British GT. Having tested the BMW Z4 GT3 in Germany, it was clearly the car for me."
Former BTCC racer Kelly will head up the commercial side of the operation. He said the team would look to expand into other European GT series in the future.
"The BMW Z4 GT3 was chosen after testing other cars eligible for this class of racing, and was the clear winner," he said. "888Optimum is a hugely exciting project and 2013 should be an outstanding year in British GT."
Richard Dutton's Fortec squad will run two Mercedes-Benz SLS AMG GT3s in the Blancpain Endurance Series and British GT in 2013.
No drivers have yet been signed but the team, which has close links to Mercedes through its Formula 3 program, will be run by Trevor Foster, who last worked with Fortec in F3 in 1995 before going to the Jordan Formula 1 team.
Team boss Richard Dutton said: "It came about when one of my old single-seater drivers said I should do GT racing, because then he could have stayed at the team!
"The idea has built from there. Mercedes asked if we wanted to do something with the GT project. It's a customer deal, but we have a very long relationship with Merc."