You should start by buying an eletric fuel pump and some fuel line. Hook it all the way back at the pick up for a FULL tank of fuel. This will eliminate about 20 possible connections for air intrusion, any rusted lines, any bad orings on quick connections, any fuel filter leaks (since it'll pressurize when engine isnt running and you'll se external leak), and eliminate the lift pump. It's the only way i found the parts truck i purchased had air intrusion at the elbow on the sending unit, i could hear it sucking air once every 10 seconds with the pump on and the engine not running. You probably have multiple air intrusion locations and fuel leaks. An electric pump that you can keep powered on the whole time will help you find them. The lift pump will only pump when the engine is rotating, and 30 seconds at a then wait 5 minutes isnt an efficient way to do it.
buy a cheap pump
http://www.amazon.com/Airtex-E8016S...1&redirect=true&ref_=oh_aui_search_detailpage
buy a roll of 5/16" fuel hose
http://www.amazon.com/Fuel-Inside-D...1&redirect=true&ref_=oh_aui_search_detailpage
start with a can of diesel, run this pump directly to your fuel filter (cut the metal line to attach it or unthread the hard line fitting and install a barb fitting)
if it starts well and runs well (don't worry about external leaks) then run the fuel hose to the top of the tank sender. If it works there then start connecting it is various places to find where air is being drawn in. It's super easy, you'd only need a wrench, a screw driver and 2 wires to connect it to the battery, or any battery, or a jumper box to run all the time while you are working. I used quick steel to repair my parts truck to just check out the engine and move it around my yard, i'd replace sender if it was actually rusted and regularly driven