The Stovebolt Site Forums The Parking Lot Big Bolts Bendix brake booster vs. electric brake booster vs. power brakes

Not all that different from my GMC system I'll bet. Have you had the hubs apart to look at the brakes themselves yet?
I looked around for a dual circut upgrade system, but didn't see anything that could move the quantity of fluid required to push those huge rear wheel cylenders.

As Grigg mentioned, the Hydroboost system seems to be a pretty simple upgrade. Same function as the HydroVac, but instead of running off manifold vacum, you mount a power steering pump and use that for motive pressure. Neat upgrade I think.

If you elect to keep it, your HydroVac is most likely going to need an extensive overhaul to become functional again. From what I understand there is an outfit over in your part of the country that does them, my local Napa parts house was going to send mine that way till I found a functional NOS part instead. Hit up Napa, local farm equipment shops, or heavy truck shops in the area and someone should be able to give you a better direction to go with it. HydroVacs are available new, still used in things like forklifts, but they carry an average $400 price tag.