I'm trying to install a fuel pressure regulator onto my SA and needed help identifying a vent line and fuel return line. Most diagrams have 4 lines and I can't seem to find any information from the engine bay side of things anyway, here's some pictures.

 

The engine bay only has the supply and return.

The 1980 Factory Service Manual is the same as the 1979 for most things except for the ignition. FSM

 

Not sure about SA's, but on an FB that lower/thinnest line (with the bolt plugging it) is the vent line from the gas tank to the charcoal canister (on SA's it's inside the air cleaner lid). The next one up is the return from carb to tank. Move up to the next bracket and the lower one (3rd from bottom) is the supply from tank to carb. Skinny one on top of that is your FR brake line. Fat one on top of sheetmetal seem is the brake booster vac line, and the skinny one with the braided hose is the clutch line (but you knew that). The only one I have on my '85 that you don't have is a charcoal can back to engine vent line. *Note - I have my engine out so all these lines are capped off, but I am positive of where they all go (on my '85).