What is this? AC Delco fuel dome....

I pulled one of these off of the inlet side of the fuel pump on my 1961 Oldsmobile 215. The fuel pump seems to be original to the car. It looks like it's hollow inside. I've replaced plenty of mechanical pumps and I've never run into one of these....any ideas? Aside from my general curiosity of what is it, my problem is with the aftermarket replacement pump I'm putting on there isn't enough clearance between the new pump and the block to put it back on.

 

"The air dome used on the Series 70 pumps provides a pocket in which fuel under pressure can compress a certain volume of air. When the pressure is relieved (pump on suction stroke) the pocket of compressed air pushes the fuel on to its destination. The air dome minimizes flow variations experienced with a two-cycle pump stroke and increases the pump output."

http://www.teambuick.com/reference/fuel_vacuum_pump.php

 

Much appreciated sir! The new one is going on without it, so I should find out soon how it runs.