Another way to avoid dealing with a 50+ year old Hydrovac design would be to adapt a Hydro-Boost system to your truck. That uses a power steering pump and hydraulic fluid, not vacuum, to make your right leg stronger. You could either stick with the original drum brakes and adapt the plumbing to the dual chamber master cylinder used with the hydroboost, or go with the entire disc/drum brake system from a suitable GVW modern truck and make it fit your original front and rear axles. Either way, you're going to be in for some custom fabrication, since the market probably just isn't out there for somebody to put together an "Easy Button" kit.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!