I dont see why not, one catch though, cast water pump or aluminum? aluminum pumps are much easier to find brackets and pulleys for, I used truck pulleys for my setup, works awesome.
is the 318 in the magnum air conditioned? if the trans is good you will need it. the car itself does not know the difference between pulleys and pumps and alternators. the PS pump will plug into your PS box , if you even have power steering. i dont