The pilot had planned to purchase the aircraft and was ferrying it to Buffalo, NY for inspection and repair. While en route, the right engine lost power. He feathered the right propeller and diverted to Turner Field. When he lowered the gear, he did not get a safe indication for the left main. Three circuits of the airport were made and altitude was lost while attempting to get a safe indication. Anticipating an imminent gear collapse, he turned to land on a grass runway, shut down and feathered the engine, and turned off the electrical power before touchdown. Subsequently, the left gear locked. With both engines and the electrical system shut down, he was unable to maintain directional control. The plane angled to the left and struck a tree and some brush. An examination revealed that two reduction gear stationary drive plate bolts, PN 68364, had failed. The magneto drive gear idler shaft had moved out of position and gears to drive both magneto cams were no longer meshing.