Those numbers don't correspond to any Johnson or Evinrude model number that I can find. I suggest you post a photo of the motor here - perhaps we can give you an estimate of tis vintage and a bit if tevhnical info about it.
Just a curiosity question ... where did you come up with the reference on his motor being a 1976 long shaft? While the number does make sense for that year/model, the info that I have says that a 1976 Johnson 6hp is a 6R76 or a 6RL76.
