Thanks for the picture; it does resemble our 62-63 Falcon. You do have a nice one! It looks like you already have a full tonneau on it which I would guess helps the aerodynamics quite a bit. If you don't carry loads in it you may be able to lower it a little depending on what kind of roads you drive on. This may do a little better job of shrouding your tires and keeping some of the air out from under the car. Of course if you put a full pan under it that will help a lot I would think.
How does one go about putting a full pan under a car? Do you turn the car upside down to work on it?
I guess I'm just too old and lazy to think about laying on my back for anything but a nice little siesta...