Yep. The bottom one is the pickup from memory. The one on top is blocked off from factory. They didn't actually use it as a return line from my knowledge. Someone else might be able to confirm this, but the mechanical pump and standard datsun fuel line is 1/4" or 6mm rough conversion.
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Ongoing Project: 1972 Datsun 510 S13 SR20Det.
http://ozdat.com/forum/viewtopic.php?f=33&t=17898
New Daily: D22 Navara (The new workhorse)
Retired 12/2016: MY98 Subaru Impreza RX
Previous Car: Restored Green 1972 Datsun 510, Hot L18