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When searching the Forums, you might try Excella HydraVac Disc Brakes to locate the threads dealing with this braking system that was available on coaches of the 1970s era. In addition to a brake controller (there is one particular controller that is suggested for use with these brakes), you will also need a vacuum connection between the tow vehicle and trailer (an auxilliary vacuum pump is usually necessary to use this braking system with a diesel powered tow vehicle). Bot the controller and vacuum connections were discussed a great length about this time last year - - see: vacuum brakes 1977 landyacht
Also, you will likely want to be prepared for the possibility that the Bargman connector on the the coach's umbilical cord will not be wired to the modern industry standard - - Airstream had its own wiring schematic in the 1970s that differs from today's industry standard. See:
1966 - 1981 Airstream Bargman Plug Wiring Schematic
Modern Industry Standard for Bargman Plug Wiring Schematic
Many Vintage coaches have been rewired to the modern standard, but not all owners have chosen to do so. I had to rewire the coach's Bargman plug prior to towing both of my coaches for the first time.
Good luck with your project!