I'm dropping a SBC in my 85 regal. I will be replacing the fuel sending unit. The sending unit that I took out the fuel tank had three outlets but I have seen a sending unit with two outlets on summit racing. I'm running a mechanical fuel pump. So can I use the sending unit with two outlets or should I use the one with three? I was told i don't need a return line. But the sending unit with two lines doesn't have a vapor line is this something I need? 
