Well one thing is for sure: if the alternator, regulator and rectifier are OK, then there MUST be something that is drawing power. There has to be, otherwise your battery wouldn't drain. DUH
Disconnect one battery clamp, and hook up an ampere meter. If there is a current flow of more than a few hundred milliamperes tops, something is off. Remember to disconnect the light under your hood when you are doing this though

I don't have a Navigator, so I don't know what size battery it has... but I bet it is more than 7Ah... You could probably run your seats all day long on that battery... and then some. The amount of power required to run some electrical gadget(s) is negligable compared to the power you need to crank that 5.4 liter engine. Your battery isn't going to choke on that.

I would not even dream of digging into that car... I don't even want to know how many miles of wire there are in it.
If the folks at Lincoln can't find it, with the complete wiring diagrams at hand... I'm sure I could figure it out if you gave me the car for a month or two though... [>:]