I replaced my alternator. My question is the old one had a ground wire running to the head. The new one does't have a terminal to hook a groud wire up to. Is this ground wire nesscessary?
Well it depends, sound like you got a onw wire alternator and the origional is a 2 wire. I think the 2nd wire is the trigger wire not really a solid ground, but some early ones did ground. If it is a ground it can to anything metal.
I agree with Dave. Sounds like your car had a dual field alt. installed previously and the car is only setup for a single field style so the 2nd field had to be grounded on the alternator that was on it to make it work. If your wiring harness only has one small green wire and the big black wire to hook up to the alt. just hook them up and your done.
If the car your refering to is the one in your avatar it looks like a 69 Dart so it is a single field system.