3/8” mechanical pump question

You would need a NOS or used fuel pump for a 70 AAR Cuda or Challenger T/A. They used 3/8 fuel lines. Maybe try Nappa or Rock Auto for replacements for this engine as they were the only small block to use it due to the Six Pack /Six Barrell setup . 1350 CFM ! It needed higher flow LOL !!
I don't believe the six pack 340's used 3/8 line. All fuel filters for those and other 70 340's are listed as 5/16.