Where's the gas
 

79"150 custom explorer 302 automatic,I have replaced every inch of fuel line doubled up on fuel filters from hard line to the carb and installed a new mech pump can't get any fuel from front tank and barely get any from rear both have plenty in tank blew air into tanks from hard line by fire wall switched inside cab front to rear got bubbles from both tanks what am I missing could switch gone bad are they known for getting stuck between tanks when switched? Any help would be great,thanks steve

fuel pump pressure test. if their is even the smallest pin hole forget about fuel flow. make sure the pump has everything it needs to work mechanically. make sure you used the right size lines as that can easily kill any pump pressure. make sure fuel can flow everywere in the system