So the Rock Auto part is close. The return line is 1/4 and the feed line is 3/8. The stock sending unit is both 3/8. I decided leaving the 30ish year old fuel lines in was a bad idea, so I ordered 50' of 3/8 to do all new. What's in there now isn't terrible, but it is at least 25 years old and I'm pretty sure rubber fuel line isn't designed to last that long. I mean, whats another $75 at this point, right? I ordered a reducer from NAPA but since the fuel lines will take a few days, I will see what the AutoZone and Advanced parts look like.