If the tires are known to be round and balanced correctly, try checking a few things. First, does the vibration get better, worse or stay the same on acceleration and deceleration? If the vibration changes, drive line vibration is more likely. Remove the drive shaft from the vehicle and move the U-joints in both planes. They should move glass smooth, not binding or tight spots. Also examine the shaft very closely for any dents or marks. No matter how slight, these will affect drive shaft balance and cause vibration.
If the vehicle has been lifted, drive shaft angle is also critical. If acceleration and deceleration have NO affect, I would suspect a tire/wheel issue. Possibly a bent wheel or even a bent axle shaft.