After Effects :: Delivering Anamorphic (2.39:1) From Video 16:9 (1.78) Format?

When I wish to deliver the look of the anamorphic format, but have source video shot in the 16:9 (1.78) format, what is the best method to convert it?
 
So far, I have read that one can imply add the letterbox bars on the top and the bottom to simulate the visual part to be in the 2.39:1 format.  I now realise, that even though visually it is the 2.39:1 format, the actual footage is still the original 1.78 format, just with black at the top and the bottom of the frame.
 
If that is okay, should one then notify film festivals and other alike that the footage is in the 1.78 format for them to project it correctly.  On the other hand, should one render only the visual part of 2.39 and then also notify them that the format is 2.39?