To the best of my knowledge, "Ram Air 3" was really applied only to the GTO where "400 HO with Ram Air Induction" was for the Firebird in the sales literature of the rime. (Or "time" if my typing was better!)
The way I remember it, Ram Air 3 was named so because it was the Ram Air system that was one step below the Ram Air 4. Ram Air 4 got its name from the 4 cold air inlets to the Ram Air system installed on the GTO with the round port head motor (L67, I believe). The lower two inlets were dropped for cost considerations, and Ram Air 3 was added to the list of GTO engine options simply because "Ram Air 4" stuck.
