I just had the same issue with a 78 wagoneer, did all the things you did replaced fuel lines and had to treat and reline the fuel tank it was full of rust, also had to replace the fuel pick up and float, after all this it still wouldn't start. I replaced the fuel pump again and check all the lines for blockage. I finally replaced the mechanical fuel pump with an electronic one. While making some final adjustments I realized the choke on the carburater was stuck closed once it was loose an the new pump hooked up it fired right up. I also rebuilt the carb, mine had been sitting for ten years. carb was really gunked up and had some minor rust. If you havn't checked it I would, some of that stuff can move around even if it has run recently and block passage ways. Good luck. It was very frustrating.