I don't know exactly, personally I would (and have) run a hydrobooster with a dual circuit master cylinder, so I haven't fully researched the replacement hydrovac units.

Seems I've seen them on 80's model ford medium duty trucks.
And on lots of imported cab over trucks usually on the right side just behind the battery box, at least that's what I think they are..

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-