You have a few choices here:
1. Stock alternator
2. Upgrade the amperage with a PA Performance alternator. You can go all the way up to 200 amps, which is what I did. Available through a number of suppliers, including American Muscle. If you go straight through PA, you can also get them custom painted for a fee.
3. Department of Boost and the 2010+ alternators. They make the argument that upgrading the amperage beyond a certain point is not helpful. They also note that the stock alternator, as well as the upgraded PA alternators, are the "6G" style, which is supposed to be far less reliable. They offer a different style (2010+) which is more amperage than stock (160 amps?), and not 6G. NOTE: The DOB one will not work with Kenne Bell SCs.
4. The Crown Vic alternator. I tried this route but, like the DOB alternator, it would not work with my Kenne Bell. They are cheap and high output. I don't know if they are 6G. You will need a ceramic spacer/isolator for the power wire, as the configuration on the back of the alternator is a little different than those made for Mustangs. There is a thread on this forum about the install.