1996 Dodge Ram Fuel Issue

I have a 96 Ram 4x4 with a 318 and my issue is I recently bought the truck. The truck runs fine with a full tank but when it gets to a half a tank of gas or less and I park it on a hill or something like that or I rock the truck real hard (im a logger and by necessity use woodland trails every day) my truck has a hard time starting and idling without me using my foot to keep it at idle untill the motor gets constant enough fuel to run or dies when rocked real hard side to side or front to rear. I am hoping you will say filter cuz that would be way more convenient then pump.