Does it still have a Quadrajet by any chance? They have the little filter on the inside. Will it easily restart when it dies, restart with difficulty, or do you have to wait for it to cool? Otherwise, are you using a transparent plastic or glass filter to monitor flow? I would urge against that. Granted, it's nice to see how it's working, but the safety of a regular metal canister filter is unparalleled and unsurpassed. I've noticed that it seems like a superfluous suggestion to some people, but my view is why take a chance? Also, it sounds like you have a rubber fuel line in the engine bay. It's important that it's routed in the most cool path possible. If it's close to something that gets hot or really hot, that could be an issue. If none of these suggestions net any progress, I would do the ole fuel pickup out of a can test if it's 100% looking like a fuel problem. If you have fresh, clean fuel coming out of the can and it still has the problem, you can rule out anything rearward of the pump leaving you just the carb and pump to worry with and vice versa. I'd also have your ignition control module tested at the parts store and thoroughly check for any vacuum leaks (either visually and/or spraying starting fluid around key areas), especially the carb base gasket. In my mind, that should effectively rule out the spark and air components leaving you with just the fuel one to worry with.
