The AC filter housings are usually marked "inlet" on the side fitting. Here's a NOS unit in my shop, AC S-6, a bit older vintage than '58, but that shouldn't matter. Makes sense, since the oil should flow from outside the filter element to inside. You may want to check to make sure the small hole in the side of the center pipe in the housing is clear.
Thank you very much! mine is so rusty you cant see the letters i honestly didnt think they were even there. now i know there to start by cleaning the lines out and checking for blockages.
