Fuel line Mod Questions- Confused

67Dart273 said
STop telliing people this WITHOUT explaining. YOU CAN NOT USE that line UNLESS you do something "else" about fuel vent. THAT 1/4" LINE IS THE FUEL TANK VENT!!!

If you want to use that existing 1/4" line you have a couple of choices

1...Look the 69/ earlier, simple, vent line into the filler neck. Modify the neck and create that style vent.

2...Use a vented cap (The stock cap IS NOT vented, it is, rather a pressure relief "pressure vacuum" cap, that relieves excess pressure, either positive pressure or vacuum pressure in the tank.) I do not care for that solution, as the filler necks are all rather special and it may be difficult to even GET a vented cap, plus, you run the risk of fuel spills out on the quarter panel.

Settle down, big guy.
The 3rd nipple on the (California only) fuel filter in question is not a liquid return, it is a "vapor separator" that (although not specifically shown in the FSM) gets plumbed into the vapor return line.

(sorry for the sideways pic, can't rotate it on my phone)
The fuel tank filler cap, however, is vented (all cars, Federal & California,'75-'76 at least) FROM THE FACTORY. It relieves pressure/vacuum variations not handled through the EEC (Evaporative Emission Control) system.

The overfill limiting valve acts as a check valve to prevent any backwash of fluid (either from tank or from vapor separator) from getting to the charcoal cannister.
Long story short- yes, he plumbs the third nipple to a tee in that line.