I just drilled a hole in a place that was clear of things and soldered it in place. I directed it away from the float and sending unit so it wouldn't wash things down. There isn't much pressure on the return side but make sure to use fuel injection high pressure hose to connect to the pump or any where else rubber line is used.
This is an old high pressure fuel pump that was installed with my system. They are pretty expensive but I bought a new one but haven't installed it yet. This one is working fine right now. It does run real quiet for electric pumps.