Dual field alternator in single field vehicle

Is this what yours looks like? The rounded off terminal is grounded to the case. I have this on my Barracuda and it works a lot better at idle than a roundback.

I didn't even know anyone was selling something like that. Where did you get it, and do you have a part no? I'm suprised they didn't just make a cheap jumper and throw it in the box, so they could sell it for "all" years.