Hello all! I have a '65 mustang with a 289 engine and a C4 trans. My differential was whining so we had new gears put in it. Now my vin plate says that the axle should be 2:80:1 but the machanic replaced them with 3:55. Now it still whines and the engine runs at high rpms at 65 mph. When the car is actually traveling at 65 mph the speedometer shows 80mph. I have not been able to find any ring and pinion set at 2:80:1. Does anyone know where i might find a set?? All help will be deeply appreciated.