A leaking float would cause the float to sink and the needle valve to stay open and cause flooding, although it should start once the gas accumulated in the intake evaporates. But if it doesn't start right away, the fuel pump would cause the gas level in the carb to be too high and either flood the engine or at least cause it to run really rich.
The check for a leaking float is usually just pull it out and shake it to listen for the gas sloshing around inside. Later Chevys used phenolic carb floats that would absorb gas and sink. Pretty common problem with those, and harder to diagnose.
It is worth checking the float and possibly rebuild the carburetor if it's leaking around the base. That could cause a vacuum leak while running and a lean condition.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.