1955 292ci stock fuel pump fuel line question

[odannyboy]

I purchased new pump to filter fuel line along with making a new 5/16" line from tank to pump.
Its then I noticed there are 4 threaded holes of different size on the fuel pump.
Top threaded hole is smaller and finer threads, like the ones on fuel filter.
Bottom threaded hole is 5/16" flared tube fitting type

Found another stock 55, their lines used the bottom threaded holes.
Why 4 holes, one set needs plugged or what do I do. Manual says nothing?
Thanks

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[74 Harley]

Is the top half of the pump a vacuum pump? Pictures would be helpful.

 

[odannyboy]

Yes thy are the two holes are on the side not on top?

 

[Jim5]

Top two holes are vacuum from carb to windshield wipers. Connect to the fuel pump with rubber hose, which connects to hard pipes.
The two bottom threaded connections are for the fuel. The connection toward the front of the car is input from tank connected with 6 inch threaded rubber hose to pipe from tank, the connection facing side of car goes up to the fuel filter and his hard piped with flare fitting..