How do the plugs look? Are you getting a nice blue spark across the electrodes on all the plugs? Sounds like they might be fouled. Had a 440 with a thermo-quad and if you pressed more than halfway to the floor to set the automatic choke, it would flood every time. Did you pull the plugs and try spinning it over a few times to dry out the cylinders? Have you checked the timing to see if maybe the distributor might have moved? If you have spark, fuel and the timing is right, it should run. I've had high mileage engines flood and wash the oil from the cylinders, causing and already worn engine to lose compression. Had to squirt a little oil in each cylinder and spin it over a few times before putting the plugs back in.