4 vent gas tank.

I need to order a new gas tank, i have a new 3/8 sender but didnt get a sender with a return line in it. If i order a new tank with the 4 vents, can i use one of the 5/16 vents as a return line? i will run the two 3/8 lines plus on 5/16 line bacn to the original vent tube in the trunk. How are these vent lines connected inside the tank?