Vibration at 70km/hr and up

So I have this vibration and it's driving me insane, it starts at 70km/hour and the button no matter what the conditions are. The vibration gets worse as the speed goes up at 120km exactly it's so bad you can hear it over the cranked radio. I feel as if the vibration is coming up through the shifter. I've tried putting on a friends set of wheels/tires, just replaced my driveshaft with a brand new one. The whole problem seemed to start after I had my syncros/clutch/flywheel/slave cylinder replaced. The rpm of the engine is not a factor as when in at 120 and put it neutral and let the Rpms drop the vibration stays.. My car is a 2005 mustang v6 if that changes anything.