Ballast Resister Needed?

If that terminal that is labeled 'GRD' is screwed so that it is solidly connected to the alternator case, then that alternator is set up for the older 1 wire field. That would be normal for a '66. So check that it is screwed hard to the case at the GRD terminal; I just can't quite tell for sure form the pix.

The regulator for the 1 wire field alternator is going to be a rectangular boxy thing with 1 screw terminal and 1 push-on terminal, not a flat pack unit with a modular type connector. The dark blue wire that goes to the ballast resistor should also connect over to the IGN terminal on the regulator; this is the 12V feed into the regulator. The other regulator terminal should connect to a green wire that then connects to the FLD terminal on the back of the alternator. All that should show up on your '66 schematic diagram.

Here is what the older regulator should look like: http://www.ebay.com/itm/like/371341382250?ul_noapp=true&chn=ps&lpid=82

Here is what the newer regulator looks like, although the color may vary: http://www.jegs.com/i/Mopar+Perform...3&cadevice=c&gclid=CLzzlIfn7ckCFZYWHwodHI8Elg