After changing both front wheel bearing assemblies, rebuilding both front axles with no affect on the sound, I finally noticed that the front right engine mount was in bad shape. Half of the rubber foot had broken off and the engine was resting on a very thin layer of rubber if at all. This seemed to jive with the problem. Only when the engine was under power (rpms up), and I was turning left (engine leaning on right mount) did I hear the sound. The fix was easy (less than an hour) and now there is no noise or vibration. There's a good explanation of it in this brickboard (search for engine mount or motor mount, I forget how to get to it).