1985 f250 with 6.9 fuel issue

[fam_mechanic]

Thanks for taking a few minutes to read my question. I am having a fuel issue. I'll explain up to the point I ended up here lol. Truck died one day. I jumped out and noticed fuel in the snow. so I figured it was a line and parked it. Today I Laid under it and found another set of fuel lines. like there WAS a rear tanks that no longer there. I just bought this truck and only see 1 fuel door in the bed figured it had 1 tank. there is no selector switch on, in, or anywhere around the dash and no empty spot where one once was. So I crank the engine and fuel pours out the open line. So im guessing a return line. I plugged them and tried to bleed the air out at the injectors. Still wont start. If I run a hose from the mechanical lift pump to a 5 gal fuel can truck runs no problem. Im getting lots of air out of the pump when I open the line to the filter housing. Here is my question. On the frame there is a unit with an electrical plug and fuel lines. im thinking its the tank selector but there is no switch. Is this possible? has ford done this ? 2 tanks 1 fill a selector and no dash switch? if so then im guessing its bad and im not sucking out of the front tank which is the only one there. Whatever has happen I was able to drive it until the other day when it all happened. Can I just remove it all and run lines just from the front tank to the lift pump and return? Any explanation of this truck would be greatly appreciated. Im sure its something simple but not being a ford guy and the 2 tank 1 fill is messing with my head a little bit lol..anyways thanks again

[65comet]

All I would come up with are guesses. (Maybe a return to get air out of the line?) Here, try a forum specific to pre 87 Ford Pickups. Someone there should be able to help you.
http://www.f150forum.com/f13/