The direct development of LaGG-3 fighter was Lavochkin La-5. By using the radial M-82 engine the speed and altitude performance of the aircraft improved. It was some 45 Km/h faster then Bf-109G. The further development (german fighters had better climb rate) led to lighter La-5FN and La-7 versions with more powerful engines.
The arnament changed to two 20 mm canons which become standard for the late versions of Lavochkin's aircraft.
More about Lavochkin LA-5 on Wikipedia
June 2009