Bigger is always better on vacuum lines- - - -that's why the big trucks with the Hydrovac used 1/2" hoses from the manifold to the reservoir tank. If you've got an option when installing a new system, use 5/16" hoses and hard lines, and hide a small reserve tank with a one-way check valve somewhere out of sight. It might not be OEM, but it will make the wipers and other vacuum-operated accessories work much better. The softball-sized round plastic vacuum reservoirs from a newer car will mount somewhere out of sight down in a fender well, etc. and won't detract from the antique appearance.
Jerry
