I'm going nuts here! My '73 2 barrel 302 usually runs fine but every now and then (now) it seems to stop pumping fuel to the carb. I put a clear filter before and after the pump and I see the one between the pump and the carb go dry. pressure drops from 5 down to 2-3 and pinching the return line seems to help some. I have replaced fuel pump twice in two years but the problem is intermittant so I don't know if it really helped. I want to go 4 barrel when mama lets me dump the cash. Any tips on what's happening and what I can do now?