I don't know a whole lot about suspensions ( anything for that matter ), but it is really tough to isolate a single bearing or bushing - if they don't show obvious signs of damage, movement beyond spec or simply too much mileage.

But since the new tires and balance seemed to cure the intensity of the vibration, maybe that is still wear the vibration is coming from.

remember the old test - vibration in steering wheel front suspsension, vibration in seat of pants rear suspension