Vince said it all. Use a GM 3 wire. 1 large 8-10ga wire, usually red, to battery from the output post on alternator, the clip will usually be a small white and a larger red. The larger red wire jump over to the alt output post with the 8-10ga that goes to battery, and hook the white smaller ga wire to the ignition switch "on" side, this turns the alternator on/off. It is also called the "exciter" lead. This is the basic GM system. There may be other positions you can use for the alternator to sense Battery charge which determines when the regulator is on or off.
As far as alternator size, you should base it on your equipment installed. If you plan on using a high power stereo system, high power lights, winch, or any other high amp drawing options, then you might want to consider the 100 amp alt. A/C and basic other functions should be fine with a standard 67amp. these are some considerations for you to determine prior to purchasing your alternator. You'll find 100 ampers can get kind of spendy as opposed to the standard 67 or so which are readily available. Regulators are built in to the alternators so nothing additional to buy. Resetable circuit breakers are a nice feature to install for additional protection. A 50amp breaker should work fine for a 67 amp alternator as the alternator will hardly ever output its full value if you keep a properly charged Battery. They trip out and come back after cooling off which will give you time to investigate a problem without frying your wiring. Just a suggestion. Hope this helps. I have wired a bunch of rods and Motorhomes this way without error or problems.
