[Rog246]

Its probably time to do an on-car balance. Ordinary wheel balancing machines are set to balance your wheel/tyres to 105kph +/- 1 or 2 k's. Once you get past about 115k's you're wasting your time getting a std dynamic balance.
The question is however where is the vib coming from ? Front or back ? It's pretty easy to tell believe it or not-If the vib is making the steering wheel move or vibrate its the front. If you're feeling it in your butt or more specifically if you go for a run in the car & when it starts look at your passenger seat and if its vibrating/moving then put your hand on the transmission tunnel behind the console & see if the vib is coming through the floor-if so its coming from the rears. The Falcon has a 2 piece tailshaft and any rear in balance of the tyres will come through there.
Hope this helps
Rog