The simplest method would be to check the Hydrovac for a model number and/or part number, and order an exact duplicate. Since you're going to use it like a truck, not a toy, I'd strongly recommend a complete rehab of the brake system: hard lines, flex lines, new linings, wheel cylinders, turn or replace the drums, etc. I'm going to also recommend that you use a trailer with its own brake system, either electric, or at least surge brakes. Electric brakes give you the option of at least slowing things down, if not stopping altogether by using manual braking with the control box in case of brake failure on the tow vehicle. I had to do that once in the middle of Nashville Tennessee interstate traffic when a brake line failed on a 59 Suburban I was driving with a trailer on behind.
Jerry
