A 12 volt draw on battery from a one wire alternator

First, how are checking the drain? Are you using a multimeter from the negative cable to the negative post when they are disconnected? You should be measuring current in amps, not volts. Any drain over 500 milliamperes will drain a battery overnight. Check the drain in that manner, and then remove fuses one at a time to isolate the circuit causing the drain. That should get you started. There are a couple circuits that are not controlled by the fuses, but start with the fused ones first, as they are easier to remove. Having the proper diagram will also help. If you do not have one, I am certain someone will chime in.