Cadillac had a V6 diesel engine back in the 1980s that had a belt driven vacuum pump. They're pretty scarce, but they used the same vacuum pump device that the V8 diesels had. One of those things and a small Freon tank for a vacuum reservoir with a one way check valve would work well with the original rear axle.
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!