Return line fitting

I installed a sump and need to add a return line. I am feeding with 3/8" aluminum from an electric fuel pump. The system will have a return from the regulator. First question is what type of fitting did you use to go into tank. Any pics of what you did? Second question is should the return be same size or one step smaller. Was thinking of running 1/2" for supply and the 3/8" I already have for return. I will be running 2x4's on a 408. Other question I have is does the vent need to be in the tank or is the original 1/4" vent in the neck going to be ok. If the original vent needs replaced what have you done for yours and what size are you using.
Thanks in advance for any help.
Rod