I cannot believe the amount of misinformation on this blog....
The newer style alternators field is controlled by the ground or negative side of the field winding and the positive side of the field winding simply goes to a good 12 volt source. You DO NOT want to ground the 2nd field wire to the newer style alternator because it is used in series with the newer style regulator which controls the field current and thus the output of the alternator. If you do ground it you will get max voltage out of the alternator at all times because you are bypassing the regulator..
The old style alternator had one field wire which went to the regulator which controlled the positive side of the field coil. The other side of the field coil was internally grounded and did not have to come out.
I do agree the later alternator is a better way to go if it's wired correctly. You do get less dimming of the headlights at idle and more current is available as needed. Only 1 wire needs to be added to make it work properly.