If you can, jack the front of the car up, place it on jack stands and remove the front wheels. Run the car up to the mph you get the vibration at, if the car still vibrates you can eliminate the tires, wheels and alignment from the equation, it usually eliminates the ball joints as well. Typically with a wheel bearing or ball joint the vibration will be more consistent but vary during different speeds and turning. I thought I had figured out what the vibration on my 92 integra was and replaced the right side axle and then the left side axle and then the wheel bearings and the lower ball joints and engine mounts and tie rod end along with two front end alignments tire rotation & balance. Why it didn't dawn on me to lift the car and run it up to speed I don't know. The vibration much like yours was usually under load around 50+ mph with the worst vibration being at 60. Hopefully yours does not turn out to be what mine is (TRANSAXLE)