Help&Advise Wtd- rear fuel tank conversion

[cypress TX 72]

I have converted to a rear tank, and need to see some pics or get some advise on the filler part.
I have fabricated a pipe to come through the bed floor behind the DS wheel tub and under the rail flange. But I am worried about the connections and the flow when putting fuel in.
The tank has a inlet of 1 1/4 OD and of course the neck that I cut off the behind the seat tank is like 3". so that creates some issues.
Also the new tank has one inlet and three vents ???????
And can anyone tell me if the new eldebrock mechanical fuel pump will pull the fuel all the way from the back of the truck.
Thanks for you help