Kevin:
I also have a JD 2010 that I have converted to Alternator and negative ground. I used the old generator output wire to charge the battery. You can simply leave the old regulator in place and pull the "gen" wire off the regulator and place it onto the "BAT" terminal along with the wire that is there. This effectively takes the regulator out of circuit and just makes it a terminal board. Using a one wire alternator, that should do it. I assume someone already changed the polarity of the ignition coil.
I didn't go the one wire alternator, but used the older style with a regulator and managed to place that regulator in the same location as the old regulator with some wire changing. DO NOT polarize an alternator, though.
If you have any questions I will be happy to answer them. I don't normally follow the threads here, so email me personally.
NOTE to all those that think EVERY manufacturer did the negative ground update: John Deere, in all their glory, did not do that until they brought out their 4020, somewhere around 1963!!! Can you imagine a 24 volt positive ground system??? That is what was used on the 4010 diesels.