12 volt system question

My tractor had a 6 volt battery in it when I got it. As it was being dug into it was determined that I have a 12 volt alternator. I am guessing that the electrical system has been converted to 12 volt and I think I want to stay with that. What are all the things that I should look for to be sure that the 12 volt system that I have is complete? What all do I need to convert if it has not already been changed over to 12 volt?

Make sure you have a ballast resistor in the coil circuit and 12 volt bulbs in the lights. Other than that, just make sure the system is negative ground with an alternator and you may have to reverse the leads on the ammeter.