mpg on my 340

Yeah it does it at every station, makes sense its a venting issue.It used to poor petrol out when driving from the top of the tank when it was 3/4 full. I traced it back to some hoses coming from the top of the tank that seemed to be cut near my diff. I pulled the hoses out and capped the top of the tank. i have a vented fuel cap as well.Where could those vent hoses have been running to in the past?

Its a 71 340 Duster