Use a 3/8" diameter vacuum hose to the booster, and install a vacuum reservoir if possible. I like to make the reservoir from a piece of 3" PVC plastic pipe about 18" long with caps glued onto both ends. It will fit nicely inside the frame rail under the cab, and if you paint it black it almost disappears. Use a T fitting threaded into one end cap and a one-way check valve between the reservoir and the intake manifold to prevent vacuum loss on a long uphill grade, etc. This also works to prevent vacuum wipers from slowing down or stopping when vacuum is low.
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!