c I agree with David as I've never seen a governor cause a completely inoperatice transmission. Did you check the fluid level only after fully warming it up and checking it with the car idling in park? You also need to cycle the shifter through the drive range a couple times. How many quarts of Dexron did you fill it with after the pan R&R? Were there any unusual noises (whining/squealing etc) emanating from the transmission? If so you may have a broken shift drum. That is by far the most common serious internal failure on this design. Previously operating the car with a bad governor is what usually causes these failures.
Rob