63 230 straight 6 fuel pump

[Montagne]

OK so I'm a newby working on my first truck. Ive got a 63 straight 6c10

I am replacing the fuel pump. When I took off the old pump and tried to install the new one it seamed as if the old one was on upside down. Now that doesnt make sense because I had the truck running. I just couldn't give it gas without it stalling. Can anyone confirm which way this thing installs? It doesnt seam to install easily the way it was but it fit just fine upside down from the way it was.

Help a newby out.