Carb suddenly acting up.

I started fouling plugs yesterday at red lights and have strong exhaust smell while stopped. Decided maybe just needed a quick tuneup so reset my timing and carb adjustments with vacuum gauge to dial it all in. Stock 76 slant six with Holley 1945.

Come to find that turning the idle fuel mixture screw all the way in doesn’t cut off the engine. I have it seated now all the way in and the car is driveable and runs great at cruise, but at stop lights definitely running to rich. Would appreciate advice on what to do to remedy or should I remove the carb and inspect? Thinking maybe bad floats? I did rebuild with brass floats last year though.