1974 MGB engine flooding

Help!
I own a 1974 chrome-bumper MGB. The starter (original) was dragging, so mechanic replaced the starter. Upon starting it after that, gasoline started pouring from the run-on valve. Removed the (original) carbon canister and ordered a new one. After installing the new canister, same thing happened PLUS the plastic connectors at the top of the canister broke off. Ordered another new canister and a run-on valve. Replaced both. When attempted to start the car, again one of the carbon canister connectors broke off. Engine smells flooded, as well. Cleaned the plugs and checked the carburetor "float" (oil is up to the top). Any ideas, please? Could it be the fuel pump / too high fuel pressure? Or perhaps could the (manual) choke be stuck open?
Thanks for any help you can provide.

1) check that fuel pressure isn't over 3 psi. 2) if pressure is ok, then check the needle valves in the float bowls. the canisters aren't the problem... you're getting gas from the carbs overflowing via the vent lines into the canisters.