Fuel return line
Tom, as I recall, my mechanic decided to run that fuel line that way instead of the other way as in your pic you sent. As I recall the input on the 1406 is on the passenger side of the carb. Here is what Tom said.
"Hi Ray, As per my post on Squarebirds regarding fuel line routes here is a photo of the fuel line on my '66, as you can see it runs up from the fuel pump, through the fuel filter and around the distributor then to the carb. Regards, Tom."
Here is the pic that Tom sent me.