Which one is better? (long)

I am putting a 904 in it because i am not going to cut up the floor for the a500/518. I will be using a Walbro fuel pump hooked to a 3/8 sending unit. I have braided line to replace the stock 5/16 line. I won't be using any emission stuff. The 96 truck this came out of is a return system. I have both filler necks, 1 with nipple and 1 w/o nipple. Fuel filter will be inline type. I thought it might be easier to use the 4 nipple tank so that i would not have to piggyback a vent on top of the return line. I guess that if i use the filler neck with the nipple, I could put the "t" in the fuel return high enough to connect with the filler neck nipple.