1966 Dart troubleshooting

Sounds just like my 69 Dart slant w/ Holley 1920. Ran like that for decades until I finally got a new carb that worked (others didn't). One guy says there is a way to blow out blockage if you remove the carb and know which bottom hole to blow thru. Another problem could be that your fuel line on the suction side is collapsing. If soft, due to ethanol, replace them w/ better "fuel injection" hose. That bit me on a long trip until I found it. However, different symptoms, the engine would start sputtering above 55 mph or going uphill, but idled fine (or as well as it did with the bad carbs).