where are you tapping for fuel pressure? I would try this, get a buddy. Cap fuel line off carb. Get some sort of fuel container and run a line from it to the carb inlet (raise above carb so it gravity feeds to carb like an I.V setup, matter of fact, that would be perfect, hook it to hood latch) run motor and keep eye on pressure. If the pump is working properly (I dont think it is) youll see no drop in pressure. If its a Edelbrock style mechanical pump, you cant take it apart and check the check valves inside. IIRC, there are 3, one pulling and 2 pushing. I had one that had the 2nd pusher come unseated. produced next to no pressure. You can also pressurize your fuel line to back flush it into the tank, that might explain a collapsed sock or just a plugged one. I took one out that was totally plugged with rust. I blew air into it and the sock split under the pressure.