Robert, I think made a pretty good guess. Based on the info so far, I'd start with checking the alternator's battery stud for a short to ground and work back from there.

8liter - Could have been fuel and yes poor running could have been dirty or looseness on a connector leading to the coil. But the poor connection is just where the heat builds, not why its drew so much current.

Lets see a photo of the battery and relay wiring when you have a chance.