Ok, you have eliminated driveline vibration, as the problem can be duplicated when the vehicle is parked. Now remove all the accessory drive belts and rev the engine to the range of the vibration. If the vibration is still there, you have eliminated all the driven components including the fan. If the vibration is gone, check the driven components.
Conner

Over the hill but still climbing.
88 Montero 2.6L auto, manual hubs, cooling fan conversion gps,recurved distributor,LSD Diff.