Factory fuel line size?

[FLYNAVY30]

On the factory return style fuel system, is the bigger line the supply or the return line? On my motor swap, I assumed the bigger of the two was the pressure and the smaller was the return, but just had a sinking feeling that I may have assumed wrong....

[Bishops Trucks]

I just looked on my truck. You are right in your assumption. Big is feed and small is return.

[FLYNAVY30]

Phewwwww.....I was just noticing that the power steering lines, the A/C lines, and the transmission oil cooler lines were all bigger on the return side than the pressure side and I started to get nervous. I've got a 6-an line all the way from the tank to the carb, and a 4-an line off the regulator back to the tank. I started to get nervous because the regulator instructions said to ensure the return line is at least as big as the pressure line. But in my application, the return line into the factory sending unit was smaller than the pressure line, so I just ran the entire system in the same size braided line with AN fittings as the factory sending unit.

[68panelman]

Thought this was fuel line thread ?. Mines 3/8 line, some are 5/16s, All my 72's are 3/8, but earlier iron is 5/16".