Sounds like trash is sloshing around inside the tank, momentarily clogging the down pipe opening. If it a partial restriction, the engine will idle just fine since the demand for fuel is low. Once you step on the gas, fuel demand will exceed supply. One time I filled my tank with gas and got a free cup of red clay with it. Stopped up the works pretty good. Check the tank for debris.
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission