That "black plastic box" probably has three leads coming out of it - one to the B+ post (black surround) and two to the field coils (paried studs with a grey surround.) Chrysler likes to use moulded rubber blocks to locate terminals that go in groups - you'll probably see something similar on your starter motor solenoid. This helps prevent mixing up the leads (not that the leads on the starter motor can be mixed up - one is 8AWG with a 3/8" ring, and the other is 14AWG with a #10 ring. That tells me something about ChryCo techs that I don't care to contemplate...)
The regulator for your alternator is actually in the PCM (Powertrain Control Module,) and not anywhere near the alternator proper. If you had a noise suppressor (capacitor/condenser,) it would be a small metal can - about 1/2" by a shade over 1" long - attached between the B+ post and the alternator case.