Hooking distributor advance to intake manifold port.

Just to add a little clarity, if you connect the vac can direct to the intake vacuum source (NOT on the carb, but intake itself) it WILL pull your advance higher at idle and cause adjustments to be necessary to compensate for advanced idle timing bringing your total timing down too low.
If you connect it to a port on the carb that only has vacuum as you open the throttle, then fine.

For economy at mid speed cruise you want ported vacuum. ( meaning vacuum comes in with throttle opening.)