fuel line help

[Burbinite]

The PO of my 72 K10 burb decided to "re-engineer" the fuel system. After removing about 25' of rubber fuel line, a marine water separater/filter and an electric "pusher" pump (all connected to the stock steel lines and mech. fuel pump) I need to know what GM had in mind. I've got a larger 3/8"? steel line running from the stock tank to just under the pass. seat along the frame rail. Then the fuel line bends out and is flared for a hose. There is a 4" gap, then another flared line continues toward the stock pump. (I'm guessing this was the stock filter location??) Please confirm.
Next, I have a 1/4" return line that does the same thing (bends out at 90° with a flare for hose(s) with a 4-5" gap) then continues toward the tank. This gap is about 12-18" behind the larger dia. line gap. What goes here? Is this stock? Any help will be greatly appreciated.