Are you using the original gas tank without a good cleanout or replacement? Gas tanks have a bad habit of forming sludge and varnish during long term storage, which can do massive engine damage when it's mixed with fresh gasoline. The most common one is valves sticking in their guides which can get severe enough to make the valves stick, bend pushrods, break rocker arms, and bend valves if they come into contact with the pistons.
NEVER, EVER, POUR FRESH GAS INTO AN OLD TANK!
I use a 2-gallon plastic gas can with a piece of flex line to the fuel pump when doing a resurrection of a barn find vehicle, and either remove the gas tank and get a radiator shop to clean it out, or replace it if a repop tank is available.
Most likely, your carb leak was caused by flooding, the result of a piece of rust or other gunk from the tank getting under the inlet needle valve in the carburetor. It's like a toilet tank fill valve that won't shut off. Removing the fuel line and running the float bowl dry allowed the gas to flush the crud out as it refilled the float bowl. You got off lucky once- - - -better deal with the gas tank now, before it bites you in the behind- - - -they almost always do!
Jerry
