Petrol tank question
 

So currently building up my Hawkeye sti and came across the two units on top of the fuel tank. The bigger one of the two has the fuel pump plug, lines and by the looks of it level gauge all on one unit. My question is what is the one at the other side? It has a pipe connection on top as well as a two wire plug, I’ve opened it up and looks to be another level gauge? Is this the case
https://cimg1.ibsrv.net/gimg/www.sco...e3309b067.jpeg

ISTR the impreza fuel tank is like an upturned U with a high point in the middle. That means fuel ends up both sides. The single fuel pump is in one side.The tanks have 2 guage senders and the return fuel goes through a venturi drawing fuel from the unpumped side to the pumped side.

https://pictures.dealer.com/s/stanle...b8ca748cf9.jpg

http://jp-carparts.com/images/subaru...mage_421_5.gif

So would I be right in saying I could just use number 1 as the supply to my swirl pot 2 as the return from swirl pot and just link both sides with a bit of hose ? Also is number 3 rollover valves which could be used as vent to atmosphere ?
https://cimg4.ibsrv.net/gimg/www.sco...cfb74a385.jpeg