1966 Mercury Comet stalls when warmed up

Just had shop put in rebuilt C4 tranny. Idle spd was too high, and tranny shifted hard. When I drive it short distances I have no problems. Its when I drive more than 4miles, or on freeway that stalling begins. My car stumbles and acts like its not getting enough fuel. If I try pumping gas pedal, it cuts out. Stalls motor. If I let off gas pedal it stays running at slower and slower rate, until attempts to maintain speed cause it to stall. What I have tried so far has failed to stop this behavior. This is what I have done so far. 1)adjusted choke cold idle spd down, adjusted both air/fuel screws one full turn out past "bog" point. So now car idles nornally, and shifts smoother also. 2)replaced air & fuel filters, added gas treatment. 3)checked fluid levels. Stalling behavior pursists.