Correct, you need to plan this out to do it right. It would be a good time to add a mega* fuse and a fuse link. I would suggest a 3G Ford style alternator (not PA Performance) of around 100A, unless you will be adding a big stereo and power windows. The thing with the ammeter is that it has to be disconnected, but you could have it converted to a functioning voltmeter and no one would ever know. The secret here is that it already is a type of voltmeter, but not what you need.
*haha, the first time I actually spelled that maga (Make America Great Again), not mega.