I have a 1985 w150 with a stock 318 2 barrel and if I come to a quick stop the motor will stall, if I step on it quick the motor will bog down and then catch up to itself and then be ok. The motor also runs very rich, to the point where if it's sitting there idling you can smell all the unburnt fuel and if you step on it you see a cloud of smoke. The thing that confuses me is that when I pulled the plugs they are all clean. This all just happened recently with no changes made to the motor. My only thoughts are a vacuum leak possibly going to the booster since a lot of the stalling happens with the braking. Any help appreciated.

Take the top off of the carb & check float/needle & seat

Is the intake manifold crossover plugged? Manifold needs to get real hot to open choke and vaporize cold fuel.