With the frame on, and my ‘63 on jack stands, I replaced the missing steel 3/8“ main fuel line, which had been carelessly substituted with a 5/16” rubber hose from the tank to the pump. Unbelievably, the PO had routed it where it flopped around on the driveshaft and and exhaust.
Replacing This 3 piece line was straightforward especially with the photos Paul shared.
The return line was another matter. It is about half a mile long and twisty like a pretzel. Eventually I it cut into 3 pieces, with the cut just before and just after the driveshaft. Used rubber fuel line to join the cuts.
The return line does carry a lot of fuel, as I discovered when I accidentally cut it while reinstalling the transmission.
The job was way bigger than I thought it would be, but working on the ground was a big part of the challenge.
I would do it over again though - to get rid of the floppy rubber line, upgrade to the correct 3/8 line, and for some reassurance on the vapor lock issues.
Just my two cents...
Chip
63 Impala 425hp