the vacume ports on the fuel pump are to give the wipers vacume when manifold vac drops due to long hills orhot roding.the lin to the manifold on the fuel pump has a check valve so when vac drops it stops the drop to wipers and provide vac for wipers(if all is working to spec) my 57ranchero has elc motor from 55 chevlooks like a bolt on(was on the ranchero when i bougt it,one of the few things that worked.

Hi there
first I do not have vacuum wipers, but i'll have a stab at it . it may encourage others to join in.
2 ports on the wiper motor  one for vacuum supply from i/l manifold and the 2nd may be just a vent to atmosphere.(which is which I have not a clue)
vacuum sources  the one on the carb for the distributor you have identified
the one on the spacer for PCV valve
the one on the manifold for brake booster and/or wiper motor
there should be 2 ports on the fuel pump one marked IN one marked OUT.  wiper motor to IN  manifold to OUT
if there are no markings   start engine and put your finger on each port one will suck and one will blow
stuey

I have a '57 Ranchero with a 292.  The windshield wiper motor has 2 vacuum ports; one on the top, one on the bottom.  From which vacuum source does each port hook up to?

I have 3 vacuum sources on my carb and intake manifold.  A very small one on the body of the carb that goes to the distributor advance diaphragm, one on a spacer between the carb and the manifold, and one on the manifold itself.  Currently the manifold and the spacer are hooked together.  The wiper motor has nothing running to it now.  I also have a vacuum source on the top of the fuel pump attached to nothing.

Thanks for any help.

Bruce