return line for EFI conversion

I finally have everything assembled and gathered for my Megasquirt conversion. The car is a '65 Barracuda with a newly rebuilt 360. All of the Megasquirt circuit boards are soldered up and tested. I'm using a GM-style 670 throttle body newly purchased from Holley. All of the sensors (water, O2, vacuum sensor, MSD input) are already present. The throttle position sensor is part of the Holley throttle body. I also have a beautiful CNC'd adapter plate for my Weiand Stealth intake.

The only hardware I don't have is a fuel return line. Since this is throttle body injection, the fuel pressure is relatively low compared to multiport injection. I can see that I can purchase new fuel sending units that have barbs with my choice of 5/6" or 3/8" inlets and outlets.

Since the pressure is relatively low, I'm thinking that maybe 5/6" in and out would be alright, or perhaps 3/8" main and 5/6" return. I'm open to opinions on this.

What I'd like to see are photos or tricks of others who have added return lines to their tanks. I haven't done anything to the existing system and won't until I know exactly what needs to be done.

Thanks,
Marcus