if it has an alternator you cant as the the tacho runs off the back of a special dynamo by a mechanical cable not electric these tractors were 12v the alternator may be old type or may have come off of a later ford with a battery temperature sensor in which case it will not charge unless one of these is fitted if i was you i would convert it to original but fit an 22amp system instead of 11amp
enginear
September 2010