Stalling

I have a 70 225 with a Holley 1920. I have a Pertonix II electronic ignition conversion. The tank and fuel pick up are new. I can drive the care for about 30 minutes then it dies, like it's not getting fuel. The last time it stalled and I was towed, there wasn't any fuel in the fuel filter (clear plastic filter). The next day the filter was half full and car started right up. Since then I removed the fuel pick up (very clean), drained the gas, replaced the fuel pump and filter, went through the carb. I readjusted the float. With the engine idling, there is very little fuel in the filter (bottom of the filter barely has any fuel). If I rev the engine and hold it at a higher RPM the level of gas doesn't change. Do you think I have blocked fuel lines? Is the tank vented? If so where? I had the trunk floor replaced and then had the stalling problem. Thanks