70' C10 break line help??

[Mrmadmanmill]

I'm Getting ready to run fuel lines and i am a little confused. Based on what i can tell from LMC, there are two sets of lines from the gas tank. I have already done a rear tank conversion, so my tank is mounted in the back as in the picture attached... what confuses me is the return line. I have a standard mechanical fuel pump and all it has is the line to the carb and an inlet from the tank.

where does the return line go to? It has been a long time since i tore my truck down and i do not remember where the return line goes... Any help or images would be greatly appreciated!!!

Thanks