http://www.californiaclassix.com/archiv ... _c620.html
Scroll about 3/4 of the way down the page and you'll see the underside.
It has been given Front Discs, but the rear drums have got a servo.
The Servo is mounted in the rear axle space and due to the length of the vacuum pipe in a relatively small bore, it appears to have a vacuum reservoir added to the vacuum line just before the Servo...
That location might work for California, but imagine the muck getting into that Air Valve on the Servo anywhere else...

It seems that in late 2010 it was sold to a customer in Wisconsin.


I've added the one image here so there is something to see if the website is removed in the future.