I heard a while back that the early '80's model BMW afm's are a direct bolt on. Question is: If they are, what would be the benefit for doing this swap, and...... if it is a direct swap are they the same manufacturer?

Yes they bolt on as in the electronic plug matches. They are the same manufactuer of fuel injection system and they come from a 2.5L 6-cyl so they only need minor tuning to work with a 2.8L They have a larger center bore than the 280Z.